# estimate

Fit conditional variance model to data

## Syntax

``EstMdl = estimate(Mdl,y)``
``````[EstMdl,EstParamCov,logL,info] = estimate(Mdl,y)``````
``EstMdl = estimate(Mdl,Tbl1)``
``````[EstMdl,EstParamCov,logL,info] = estimate(Mdl,Tbl1)``````
``[___] = estimate(___,Name,Value)``

## Description

example

````EstMdl = estimate(Mdl,y)` returns the fully specified, estimated conditional variance model `EstMdl`. This model stores the estimated parameter values resulting from fitting the conditional variance model `Mdl` to the observed univariate time series `y` by using maximum likelihood. `EstMdl` and `Mdl` are the same model type and have the same structure (see `garch`, `egarch`, and `gjr`).```

example

``````[EstMdl,EstParamCov,logL,info] = estimate(Mdl,y)``` also returns the estimated variance-covariance matrix associated with estimated parameters `EstParamCov`, the optimized loglikelihood objective function `logL`, and a data structure of summary information `info`.```

example

````EstMdl = estimate(Mdl,Tbl1)` fits the conditional variance model `Mdl` to response variable in the input table or timetable `Tbl1`, which contains time series data, and returns the fully specified, estimated conditional variance model `EstMdl`. `estimate` selects the response variable named in `Mdl.SeriesName` or the sole variable in `Tbl1`. To select a different response variable in `Tbl1` to fit the model to, use the `ResponseVariable` name-value argument. (since R2023a)```

example

``````[EstMdl,EstParamCov,logL,info] = estimate(Mdl,Tbl1)``` also returns the estimated variance-covariance matrix associated with estimated parameters `EstParamCov`, the optimized loglikelihood objective function `logL`, and a data structure of summary information `info`. (since R2023a)```

example

````[___] = estimate(___,Name,Value)` specifies options using one or more name-value arguments in addition to any of the input argument combinations in previous syntaxes. `estimate` returns the output argument combination for the corresponding input arguments. For example, `estimate(Mdl,y,Y0=y0)` fits the conditional variance model `Mdl` to the vector of response data `y`, and specifies the vector of presample response data `y0`.Supply all input data using the same data type. Specifically: If you specify the numeric vector `y`, optional data sets must be numeric arrays and you must use the appropriate name-value argument. For example, to specify a presample, set the `Y0` name-value argument to a numeric matrix of presample data.If you specify the table or timetable `Tbl1`, optional data sets must be tables or timetables, respectively, and you must use the appropriate name-value argument. For example, to specify a presample, set the `Presample` name-value argument to a table or timetable of presample data. ```

## Examples

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Fit a GARCH(1,1) model to a simulated vector of data.

Simulate 500 data points from the GARCH(1,1) model

`${y}_{t}={\epsilon }_{t},$`

where ${\epsilon }_{t}={\sigma }_{t}{z}_{t}$ and

`${\sigma }_{t}^{2}=0.0001+0.5{\sigma }_{t-1}^{2}+0.2{\epsilon }_{t-1}^{2}.$`

Use the default Gaussian innovation distribution for ${z}_{t}$.

```Mdl0 = garch(Constant=0.0001,GARCH=0.5,ARCH=0.2); rng("default") % For reproducibility [v,y] = simulate(Mdl0,500);```

The output `v` contains simulated conditional variances. `y` is a column vector of simulated responses (innovations).

Specify a GARCH(1,1) model with unknown coefficients, and fit it to the series `y`.

```Mdl = garch(1,1); EstMdl = estimate(Mdl,y)```
``` GARCH(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue __________ _____________ __________ __________ Constant 9.8911e-05 3.0726e-05 3.2191 0.001286 GARCH{1} 0.45394 0.11193 4.0557 4.9986e-05 ARCH{1} 0.26374 0.056931 4.6326 3.6111e-06 ```
```EstMdl = garch with properties: Description: "GARCH(1,1) Conditional Variance Model (Gaussian Distribution)" SeriesName: "Y" Distribution: Name = "Gaussian" P: 1 Q: 1 Constant: 9.89107e-05 GARCH: {0.453936} at lag [1] ARCH: {0.263739} at lag [1] Offset: 0 ```

The result is a new `garch` model called `EstMdl`. The parameter estimates in `EstMdl` resemble the parameter values that generated the simulated data.

Fit an EGARCH(1,1) model to simulated data.

Simulate 500 data points from an EGARCH(1,1) model

`${y}_{t}={\epsilon }_{t},$`

where ${\epsilon }_{t}={\sigma }_{t}{z}_{t},$ and

`$\mathrm{log}{\sigma }_{t}^{2}=0.001+0.7\mathrm{log}{\sigma }_{t-1}^{2}+0.5\left[\frac{|{\epsilon }_{t-1}|}{{\sigma }_{t-1}}-\sqrt{\frac{2}{\pi }}\right]-0.3\left(\frac{{\epsilon }_{t-1}}{{\sigma }_{t-1}}\right)$`

(the distribution of ${z}_{t}$ is Gaussian).

```Mdl0 = egarch(Constant=0.001,GARCH=0.7, ... ARCH=0.5,Leverage=-0.3); rng("default") % For reproducibility [v,y] = simulate(Mdl0,500);```

The output `v` contains simulated conditional variances. `y` is a column vector of simulated responses (innovations).

Specify an EGARCH(1,1) model with unknown coefficients, and fit it to the series `y`.

```Mdl = egarch(1,1); EstMdl = estimate(Mdl,y)```
``` EGARCH(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue ___________ _____________ __________ __________ Constant -0.00063867 0.031698 -0.020149 0.98392 GARCH{1} 0.70506 0.067359 10.467 1.2221e-25 ARCH{1} 0.56774 0.074746 7.5956 3.063e-14 Leverage{1} -0.32116 0.053345 -6.0204 1.7399e-09 ```
```EstMdl = egarch with properties: Description: "EGARCH(1,1) Conditional Variance Model (Gaussian Distribution)" SeriesName: "Y" Distribution: Name = "Gaussian" P: 1 Q: 1 Constant: -0.00063867 GARCH: {0.705065} at lag [1] ARCH: {0.567741} at lag [1] Leverage: {-0.321158} at lag [1] Offset: 0 ```

The result is a new `egarch` model called `EstMdl`. The parameter estimates in `EstMdl` resemble the parameter values that generated the simulated data.

Fit a GJR(1,1) model to simulated data.

Simulate 500 data points from a GJR(1,1) model.

`${y}_{t}={\epsilon }_{t},$`

where ${\epsilon }_{t}={\sigma }_{t}{z}_{t}$ and

`${\sigma }_{t}^{2}=0.001+0.5{\sigma }_{t-1}^{2}+0.2{\epsilon }_{t-1}^{2}+0.2I\left[{\epsilon }_{t-1}<0\right]{\epsilon }_{t-1}^{2}.$`

Use the default Gaussian innovation distribution for ${z}_{t}$.

```Mdl0 = gjr(Constant=0.001,GARCH=0.5, ... ARCH=0.2,Leverage=0.2); rng("default") % For reproducibility [v,y] = simulate(Mdl0,500);```

The output `v` contains simulated conditional variances. `y` is a column vector of simulated responses (innovations).

Specify a GJR(1,1) model with unknown coefficients, and fit it to the series `y`.

```Mdl = gjr(1,1); EstMdl = estimate(Mdl,y)```
``` GJR(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue __________ _____________ __________ __________ Constant 0.00097382 0.00025135 3.8743 0.00010694 GARCH{1} 0.46056 0.071793 6.4151 1.4077e-10 ARCH{1} 0.24126 0.063409 3.8047 0.00014196 Leverage{1} 0.25051 0.11265 2.2237 0.026171 ```
```EstMdl = gjr with properties: Description: "GJR(1,1) Conditional Variance Model (Gaussian Distribution)" SeriesName: "Y" Distribution: Name = "Gaussian" P: 1 Q: 1 Constant: 0.000973819 GARCH: {0.460555} at lag [1] ARCH: {0.241256} at lag [1] Leverage: {0.250507} at lag [1] Offset: 0 ```

The result is a new `gjr` model called `EstMdl`. The parameter estimates in `EstMdl` resemble the parameter values that generated the simulated data.

Fit a GARCH(1,1) model to the daily close NASDAQ Composite Index returns.

Load the NASDAQ data included with the toolbox. Convert the index to returns.

```load Data_EquityIdx nasdaq = DataTable.NASDAQ; y = price2ret(nasdaq); T = length(y); figure plot(y) xlim([0,T]) title("NASDAQ Returns")```

The returns exhibit volatility clustering.

Specify a GARCH(1,1) model, and fit it to the series. One presample innovation is required to initialize this model. Use the first observation of `y` as the necessary presample innovation.

```Mdl = garch(1,1); [EstMdl,EstParamCov] = estimate(Mdl,y(2:end),E0=y(1))```
``` GARCH(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue __________ _____________ __________ __________ Constant 1.9987e-06 5.4228e-07 3.6857 0.00022807 GARCH{1} 0.88356 0.0084341 104.76 0 ARCH{1} 0.10903 0.0076472 14.257 4.041e-46 ```
```EstMdl = garch with properties: Description: "GARCH(1,1) Conditional Variance Model (Gaussian Distribution)" SeriesName: "Y" Distribution: Name = "Gaussian" P: 1 Q: 1 Constant: 1.99867e-06 GARCH: {0.883563} at lag [1] ARCH: {0.109027} at lag [1] Offset: 0 ```
```EstParamCov = 3×3 10-4 × 0.0000 -0.0000 0.0000 -0.0000 0.7113 -0.5343 0.0000 -0.5343 0.5848 ```

The output `EstMdl` is a new `garch` model with estimated parameters.

Use the output variance-covariance matrix to calculate the estimate standard errors.

`se = sqrt(diag(EstParamCov))`
```se = 3×1 0.0000 0.0084 0.0076 ```

These are the standard errors shown in the estimation output display. They correspond (in order) to the constant, GARCH coefficient, and ARCH coefficient.

Fit an EGARCH(1,1) model to the daily close NASDAQ Composite Index returns.

Load the NASDAQ data included with the toolbox. Convert the index to returns.

```load Data_EquityIdx nasdaq = DataTable.NASDAQ; y = price2ret(nasdaq); T = length(y); figure plot(y) xlim([0,T]) title("NASDAQ Returns")```

The returns exhibit volatility clustering.

Specify an EGARCH(1,1) model, and fit it to the series. One presample innovation is required to initialize this model. Use the first observation of `y` as the necessary presample innovation.

```Mdl = egarch(1,1); [EstMdl,EstParamCov] = estimate(Mdl,y(2:end),E0=y(1))```
``` EGARCH(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue _________ _____________ __________ __________ Constant -0.13478 0.022092 -6.101 1.0539e-09 GARCH{1} 0.98391 0.0024221 406.22 0 ARCH{1} 0.19964 0.013966 14.296 2.3323e-46 Leverage{1} -0.060243 0.005647 -10.668 1.4355e-26 ```
```EstMdl = egarch with properties: Description: "EGARCH(1,1) Conditional Variance Model (Gaussian Distribution)" SeriesName: "Y" Distribution: Name = "Gaussian" P: 1 Q: 1 Constant: -0.134784 GARCH: {0.983909} at lag [1] ARCH: {0.199645} at lag [1] Leverage: {-0.0602431} at lag [1] Offset: 0 ```
```EstParamCov = 4×4 10-3 × 0.4881 0.0533 -0.1018 0.0106 0.0533 0.0059 -0.0118 0.0017 -0.1018 -0.0118 0.1950 0.0016 0.0106 0.0017 0.0016 0.0319 ```

The output `EstMdl` is a new `egarch` model with estimated parameters.

Use the output variance-covariance matrix to calculate the estimate standard errors.

`se = sqrt(diag(EstParamCov))`
```se = 4×1 0.0221 0.0024 0.0140 0.0056 ```

These are the standard errors shown in the estimation output display. They correspond (in order) to the constant, GARCH coefficient, ARCH coefficient, and leverage coefficient.

Since R2023a

Fit a GARCH(1,1) model to the daily close NASDAQ Composite Index returns. Supply a timetable of data and specify the series for the fit.

Load the NASDAQ data included with the toolbox. Convert the index to returns.

```load Data_EquityIdx DTTRet = price2ret(DataTimeTable); T = height(DTTRet); figure plot(DTTRet.Time,DTTRet.NASDAQ) title("NASDAQ Returns")```

The returns exhibit volatility clustering.

Specify a GARCH(1,1) model, and fit it to the series. Specify the entire timetable of returns and select the variable containing the NASDAQ returns.

```Mdl = garch(1,1); [EstMdl,EstParamCov] = estimate(Mdl,DTTRet,ResponseVariable="NASDAQ")```
``` GARCH(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue __________ _____________ __________ __________ Constant 2.0101e-06 5.4314e-07 3.7008 0.0002149 GARCH{1} 0.8833 0.0084528 104.5 0 ARCH{1} 0.10919 0.007662 14.251 4.4112e-46 ```
```EstMdl = garch with properties: Description: "GARCH(1,1) Conditional Variance Model (Gaussian Distribution)" SeriesName: "Y" Distribution: Name = "Gaussian" P: 1 Q: 1 Constant: 2.01006e-06 GARCH: {0.883295} at lag [1] ARCH: {0.109192} at lag [1] Offset: 0 ```
```EstParamCov = 3×3 10-4 × 0.0000 -0.0000 0.0000 -0.0000 0.7145 -0.5367 0.0000 -0.5367 0.5871 ```

Since R2023a

Fit a GJR(1,1) model to the daily close NASDAQ Composite Index returns. Specify in-sample and presample data in a timetable.

Load the NASDAQ data included with the toolbox. Convert the index to returns.

```load Data_EquityIdx DTTRet = price2ret(DataTimeTable); T = height(DTTRet); figure plot(DTTRet.Time,DTTRet.NASDAQ) title("NASDAQ Returns")```

The returns exhibit volatility clustering.

Because $\mathrm{max}\left(p,q\right)=1$, one presample innovation is required to initialize this model. Partition the timetable of data into sets containing required presample and insample observations.

```numpreobs = 1; DTTRetPresample = DTTRet(1:numpreobs,:); DTTRetInsample = DTTRet((numpreobs+1):end,:);```

Specify a GJR(1,1) model, and fit it to the series. Specify the timetables of NASDAQ returns for the required presample innovations and in-sample data.

```Mdl = gjr(1,1); [EstMdl,EstParamCov] = estimate(Mdl,DTTRetInsample,Presample=DTTRetPresample, ... ResponseVariable="NASDAQ",PresampleInnovationVariable="NASDAQ");```
``` GJR(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue __________ _____________ __________ __________ Constant 2.4569e-06 5.6863e-07 4.3208 1.5549e-05 GARCH{1} 0.88133 0.0094909 92.86 0 ARCH{1} 0.06414 0.0092031 6.9693 3.1843e-12 Leverage{1} 0.088796 0.0099186 8.9525 3.4746e-19 ```

The output `EstMdl` is a new `gjr` model with estimated parameters.

Use the output variance-covariance matrix to calculate the estimate standard errors.

`se = sqrt(diag(EstParamCov))`
```se = 4×1 0.0000 0.0095 0.0092 0.0099 ```

These are the standard errors shown in the estimation output display. They correspond (in order) to the constant, GARCH coefficient, ARCH coefficient, and leverage coefficient.

## Input Arguments

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Conditional variance model containing unknown parameters, specified as a `garch`, `egarch`, or `gjr` model object.

`NaN`-valued elements in properties indicate unknown, estimable parameters. Specified elements indicate equality constraints on parameters in model estimation.

Observed response data yt, to which the conditional variance model `Mdl` is fit, specified as a `numobs`-by-1 numeric column vector. `y` represents `numobs` observations of a univariate time series.

`y` is usually a mean 0 series of innovations or residuals and conditional variance characterized by the conditional variance model `Mdl`. In this case, `y` is a continuation of the innovation series `E0`.

`y` can also represent an innovation series with mean 0 plus an offset. A nonzero value of `Mdl.Offset` signals the inclusion of an offset in `Mdl`.

The last observation of `y` is the latest observation.

Data Types: `double`

Since R2023a

Time series data containing response variable yt, to which `estimate` fits the conditional variance model `Mdl`, specified as a table or timetable with `numvars` variables and `numobs` rows. You can optionally select a response variable by using the `ResponseVariable` name-value argument.

The selected response variable in `Tbl1` is a numeric vector representing a single path of `numobs` observations.

Each row is an observation, and measurements in each row occur simultaneously.

If `Tbl1` is a timetable, it must represent a sample with a regular datetime time step (see `isregular`), and the datetime vector `Tbl1.Time` must be strictly ascending or descending.

If `Tbl1` is a table, the last row contains the latest observation.

### Name-Value Arguments

Specify optional pairs of arguments as `Name1=Value1,...,NameN=ValueN`, where `Name` is the argument name and `Value` is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose `Name` in quotes.

Example: `Display="iter",E0=[0.1; 0.05]` specifies to display iterative optimization information, and `[0.05; 0.1]` as presample innovations.

For GARCH, EGARCH, and GJR Models

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Since R2023a

Variable to select from `Tbl1` to treat as the response variable yt, specified as one of the following data types:

• String scalar or character vector containing a variable name in `Tbl1.Properties.VariableNames`

• Variable index (integer) to select from `Tbl1.Properties.VariableNames`

• A length `numvars` logical vector, where ```ResponseVariable(j) = true``` selects variable `j` from `Tbl1.Properties.VariableNames`, and `sum(ResponseVariable)` is `1`

The selected variable must be a numeric vector and cannot contain missing values (`NaN`).

If `Tbl1` has one variable, the default specifies that variable. Otherwise, the default matches the variable to name in `Mdl.SeriesName`.

Example: `ResponseVariable="StockRate2"`

Example: `ResponseVariable=[false false true false]` or `ResponseVariable=3` selects the third table variable as the response variable.

Data Types: `double` | `logical` | `char` | `cell` | `string`

Presample innovations εt, specified as a `numpreobs`-by-1 numeric column vector. The presample innovations provide initial values for the innovations process of the conditional variance model `Mdl`. The presample innovations derive from a distribution with mean 0. Use `E0` only when you supply the vector of response data `y`.

`numpreobs` is the number of presample observations. Each row is a presample observation. The last row contains the latest presample observation. `numpreobs` must be at least `Mdl.Q`. If `numpreobs` > `Mdl.Q`, `estimate` uses the latest required number of observations only. The last element or row contains the latest observation.

The defaults are:

• For GARCH(P,Q) and GJR(P,Q) models, `estimate` sets any necessary presample innovations to the square root of the average squared value of the offset-adjusted response series `y`.

• For EGARCH(P,Q) models, `estimate` sets any necessary presample innovations to zero.

Data Types: `double`

Presample conditional variances σt2, specified as a `numpreobs`-by-1 positive column vector. `V0` provides initial values for conditional variance process of the conditional variance model `Mdl`. Use `V0` only when you supply the vector of response data `y`.

Each row is a presample observation. The last row contains the latest presample observation.

• For GARCH(P,Q) and GJR(P,Q) models, `numpreobs` must be at least `Mdl.P`.

• For EGARCH(P,Q) models,`numpreobs` must be at least `max([Mdl.P Mdl.Q])`.

If `numpreobs` exceeds the minimum number, `estimate` uses only the latest observations. The last element or row contains the latest observation.

By default, `estimate` sets the necessary presample conditional variances to the average squared value of the offset-adjusted response series `y`.

Data Types: `double`

Since R2023a

Presample data for innovations εt or conditional variances σt2 to initialize the model for estimation, specified as a table or timetable, the same type as `Tbl1`, with `numprevars` variables and `numpreobs` rows. Use `Presample` only when you supply a table or timetable of data `Tbl1`.

Each selected variable is a single path of `numpreobs` observations representing the presample of innovations or conditional variances for the selected response variable in `Tbl1`.

Each row is a presample observation, and measurements in each row occur simultaneously. `numpreobs` must be one of the following values:

• `Mdl.P` when `Presample` provides only presample conditional variances

• `Mdl.Q` when `Presample` provides only presample innovations

• `max([Mdl.P Mdl.Q])` when `Presample` provides presample innovations and conditional variances

If you supply more rows than necessary, `estimate` uses the latest required number of observations only.

If `Presample` is a timetable, all the following conditions must be true:

• `Presample` must represent a sample with a regular datetime time step (see `isregular`).

• The inputs `Tbl1` and `Presample` must be consistent in time such that `Presample` immediately precedes `Tbl1` with respect to the sampling frequency and order.

• The datetime vector of sample timestamps `Presample.Time` must be ascending or descending.

If `Presample` is a table, the last row contains the latest presample observation.

By default:

• For GARCH(P,Q) and GJR(P,Q) models, `estimate` sets any necessary presample innovations to the square root of the average squared value of the offset-adjusted response series `y`.

• For EGARCH(P,Q) models, `estimate` sets any necessary presample innovations to zero.

• `estimate` sets the necessary presample conditional variances to the average squared value of the offset-adjusted response series.

If you specify the `Presample`, you must specify the presample innovations or conditional variance variable names by using the `PresampleInnovationVariable` or `PresampleVarianceVariable` name-value argument.

Since R2023a

Variable of `Presample` containing data for the presample innovations εt, specified as one of the following data types:

• String scalar or character vector containing a variable name in `Presample.Properties.VariableNames`

• Variable index (integer) to select from `Presample.Properties.VariableNames`

• A length `numprevars` logical vector, where ```PresampleInnovationVariable(j) = true``` selects variable `j` from `Presample.Properties.VariableNames`, and `sum(PresampleInnovationVariable)` is `1`

The selected variable must be a numeric vector and cannot contain missing values (`NaN`).

If you specify presample innovations data by using the `Presample` name-value argument, you must specify `PresampleInnovationVariable`.

Example: `PresampleInnovationVariable="StockRateInnov0"`

Example: ```PresampleInnovationVariable=[false false true false]``` or `PresampleInnovationVariable=3` selects the third table variable as the presample innovations variable.

Data Types: `double` | `logical` | `char` | `cell` | `string`

Since R2023a

Variable of `Presample` containing data for the presample conditional variances σt2, specified as one of the following data types:

• String scalar or character vector containing a variable name in `Presample.Properties.VariableNames`

• Variable index (integer) to select from `Presample.Properties.VariableNames`

• A length `numprevars` logical vector, where `PresampleVarianceVariable(j) = true` selects variable `j` from `Presample.Properties.VariableNames`, and `sum(PresampleVarianceVariable)` is `1`

The selected variable must be a numeric vector and cannot contain missing values (`NaN`).

If you specify presample conditional variance data by using the `Presample` name-value argument, you must specify `PresampleVarianceVariable`.

Example: `PresampleVarianceVariable="StockRateVar0"`

Example: `PresampleVarianceVariable=[false false true false]` or `PresampleVarianceVariable=3` selects the third table variable as the presample conditional variance variable.

Data Types: `double` | `logical` | `char` | `cell` | `string`

Optimization options, specified as an `optimoptions` optimization controller. For details on modifying the default values of the optimizer, see `optimoptions` or `fmincon` in Optimization Toolbox™.

For example, to change the constraint tolerance to `1e-6`, set ```options = optimoptions(@fmincon,ConstraintTolerance=1e-6,Algorithm="sqp")```. Then, pass `Options` into `estimate` using `Options=options`.

By default, `estimate` uses the same default options as `fmincon`, except `Algorithm` is `"sqp"` and `ConstraintTolerance` is `1e-7`.

Initial conditional variance model constant estimate, specified as a numeric scalar.

For GARCH(P,Q) and GJR(P,Q) models, `Constant0` must be a positive scalar.

By default, `estimate` derives initial estimates using standard time series techniques.

Data Types: `double`

Initial coefficient estimates for past conditional variance terms, specified as a numeric vector.

• For GARCH(P,Q) and GJR(P,Q) models:

• `GARCH0` must be a numeric vector containing nonnegative elements.

• `GARCH0` contains the initial coefficient estimates associated with the past conditional variance terms that compose the GARCH polynomial.

• For EGARCH(P,Q) models,`GARCH0` contains the initial coefficient estimates associated with past log conditional variance terms that compose the GARCH polynomial.

The number of coefficients in `GARCH0` must equal the number of lags associated with nonzero coefficients in the GARCH polynomial, as specified in the `GARCHLags` property of `Mdl`.

By default, `estimate` derives initial estimates using standard time series techniques.

Data Types: `double`

Initial coefficient estimates corresponding to past innovation terms, specified as a numeric vector.

• For GARCH(P,Q) and GJR(P,Q) models:

• `ARCH0` must be a numeric vector containing nonnegative elements.

• `ARCH0` contains the initial coefficient estimates associated with the past squared innovation terms that compose the ARCH polynomial.

• By default, `estimate` derives initial estimates using standard time series techniques.

• For EGARCH(P,Q) models:

• `ARCH0` contains the initial coefficient estimates associated with the magnitude of the past standardized innovations that compose the ARCH polynomial.

• By default, `estimate` sets the initial coefficient estimate associated with the first nonzero lag in the model to a small positive value. All other values are zero.

The number of coefficients in `ARCH0` must equal the number of lags associated with nonzero coefficients in the ARCH polynomial, as specified in the `ARCHLags` property of `Mdl`.

Data Types: `double`

Initial innovation mean model offset estimate, specified as a scalar.

By default, `estimate` sets the initial estimate to the sample mean of `y`.

Data Types: `double`

Initial estimate of the t-distribution degrees-of-freedom parameter ν, specified as a positive scalar. `DoF0` must exceed 2.

Data Types: `double`

Command Window display option, specified as one or more of the values in this table.

ValueInformation Displayed
`"diagnostics"`Optimization diagnostics
`"full"`Maximum likelihood parameter estimates, standard errors, t statistics, iterative optimization information, and optimization diagnostics
`"iter"`Iterative optimization information
`"off"`None
`"params"`Maximum likelihood parameter estimates, standard errors, and t statistics and p-values of coefficient significance tests

Example: `Display="off"` is well suited for running a simulation that estimates many models.

Example: `Display=["params" "diagnostics"]` displays all estimation results and the optimization diagnostics.

Data Types: `char` | `cell` | `string`

For EGARCH and GJR Models

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Initial coefficient estimates past leverage terms, specified as a numeric vector.

For EGARCH(P,Q) models, `Leverage0` contains the initial coefficient estimates associated with past standardized innovation terms that compose the leverage polynomial.

For GJR(P,Q) models, `Leverage0` contains the initial coefficient estimates associated with past, squared, negative innovations that compose the leverage polynomial.

The number of coefficients in `Leverage0` must equal the number of lags associated with nonzero coefficients in the leverage polynomial (`Leverage`), as specified in `LeverageLags`.

By default, `estimate` sets the initial estimate of the coefficient associated with the first non-zero lag in the model to a small negative value, and it sets all others initial coefficients to zero.

Data Types: `double`

Note

• `NaN` values in `Y`, `E0`, and `V0` indicate missing values. `estimate` removes missing values from specified data by list-wise deletion.

• For the presample, `estimate` horizontally concatenates `E0` and `V0`, and then it removes any row of the concatenated matrix containing at least one `NaN`.

• For the estimation sample, `estimate` removes any row of `Y` containing at least one `NaN`.

This type of data reduction reduces the effective sample size and can create an irregular time series.

• For numeric data inputs, `estimate` assumes that you synchronize the presample data such that the latest observations occur simultaneously.

• `estimate` issues an error when any table or timetable input contains missing values.

## Output Arguments

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Conditional variance model containing parameter estimates, returned as a `garch`, `egarch`, or `gjr` model object. `estimate` uses maximum likelihood to calculate all parameter estimates not constrained by `Mdl` (i.e., constrained parameters have known values).

`EstMdl` is a fully specified conditional variance model. To infer conditional variances for diagnostic checking, pass `EstMdl` to `infer`. To simulate or forecast conditional variances, pass `EstMdl` to `simulate` or `forecast`, respectively.

Variance-covariance matrix of maximum likelihood estimates of model parameters known to the optimizer, returned as a numeric matrix.

The rows and columns associated with any parameters estimated by maximum likelihood contain the covariances of estimation error. The standard errors of the parameter estimates are the square root of the entries along the main diagonal.

The rows and columns associated with any parameters that are held fixed as equality constraints contain `0`s.

`estimate` uses the outer product of gradients (OPG) method to perform covariance matrix estimation.

`estimate` orders the parameters in `EstParamCov` as follows:

• Constant

• Nonzero GARCH coefficients at positive lags

• Nonzero ARCH coefficients at positive lags

• For EGARCH and GJR models, nonzero leverage coefficients at positive lags

• Degrees of freedom (t innovation distribution only)

• Offset (models with nonzero offset only)

Data Types: `double`

Optimized loglikelihood objective function value, returned as a scalar.

Data Types: `double`

Optimization summary, returned as a structure array with the fields described in this table.

FieldDescription
`exitflag`Optimization exit flag (see `fmincon` in Optimization Toolbox)
`options`Optimization options controller (see `optimoptions` and `fmincon` in Optimization Toolbox)
`X`Vector of final parameter estimates
`X0`Vector of initial parameter estimates

For example, you can display the vector of final estimates by entering `info.X` in the Command Window.

Data Types: `struct`

## Algorithms

• If you do not specify the presample data (`E0` and `V0` , or `Presample`), `estimate` derives the necessary presample observations from the unconditional, or long-run, variance of the offset-adjusted response process.

• For all conditional variance models, presample conditional variances are the sample average of the squared disturbances of the offset-adjusted response data.

• For GARCH(P,Q) and GJR(P,Q) models, presample innovations are the square root of the average squared value of the offset-adjusted response data.

• For EGARCH(P,Q) models, presample innovations are `0`.

These specifications minimize initial transient effects.

• If you specify a value for the `Display` name-value argument, it takes precedence over the specifications of the optimization options `Diagnostics` and `Display`. Otherwise, `estimate` honors all selections related to the display of optimization information in the optimization options.

## References

[1] Bollerslev, Tim. “Generalized Autoregressive Conditional Heteroskedasticity.” Journal of Econometrics 31 (April 1986): 307–27. https://doi.org/10.1016/0304-4076(86)90063-1.

[2] Bollerslev, Tim. “A Conditionally Heteroskedastic Time Series Model for Speculative Prices and Rates of Return.” The Review of Economics and Statistics 69 (August 1987): 542–47. https://doi.org/10.2307/1925546.

[3] Box, G. E. P., G. M. Jenkins, and G. C. Reinsel. Time Series Analysis: Forecasting and Control. 3rd ed. Englewood Cliffs, NJ: Prentice Hall, 1994.

[4] Enders, W. Applied Econometric Time Series. Hoboken, NJ: John Wiley & Sons, 1995.

[5] Engle, Robert. F. “Autoregressive Conditional Heteroscedasticity with Estimates of the Variance of United Kingdom Inflation.” Econometrica 50 (July 1982): 987–1007. https://doi.org/10.2307/1912773.

[6] Glosten, L. R., R. Jagannathan, and D. E. Runkle. “On the Relation between the Expected Value and the Volatility of the Nominal Excess Return on Stocks.” The Journal of Finance. Vol. 48, No. 5, 1993, pp. 1779–1801.

[7] Greene, W. H. Econometric Analysis. 3rd ed. Upper Saddle River, NJ: Prentice Hall, 1997.

[8] Hamilton, James D. Time Series Analysis. Princeton, NJ: Princeton University Press, 1994.

## Version History

Introduced in R2012a

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