# Documentation

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# rfinterp1

Interpolate network parameter data at new frequencies

## Syntax

``objnew = rfinterp1(objold,newfreq)``
``objnew = rfinterp1(objold,newfreq,'extrap')``

## Description

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````objnew = rfinterp1(objold,newfreq)` interpolates the network parameter data in `objold` at the specified frequencies, `newfreq`, storing the results in `objnew`. `rfinterp1` uses the MATLAB® function `interp1` to interpolate each individual `(i,j)` parameter of `objold` to the new frequencies.If any value of the specified frequency is outside of the range specified by `objold.frequencies`, then `rfinterp1` inserts `NaNs` into `objnew` for those frequency values.```
````objnew = rfinterp1(objold,newfreq,'extrap')` interpolates as above, but if any value of the specified frequency values are outside of the range of `objold.frequencies`, then `rfinterp1` will extrapolate flat using the nearest values in the frequency range.```

## Examples

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Read the data from the file `default.s2p` into an S-parameter object.

```hnet = sparameters('default.s2p'); ```

Interpolate the data at a specified set of frequencies.

```freq = [1.2:0.2:2.8]*1e9; hnet2 = rfinterp1(hnet,freq) ```
```hnet2 = sparameters: S-parameters object NumPorts: 2 Frequencies: [9x1 double] Parameters: [2x2x9 double] Impedance: 50 rfparam(obj,i,j) returns S-parameter Sij ```

## Input Arguments

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Data to interpolate, specified as an RF Toolbox™ network parameter object. `objold` must be a network parameter object of the following types: s-parameters, t-parameters, y-parameters, z-parameters, h-parameters, g-parameters, or abcd-parameters.

Frequencies of interpolation, specified as a vector of positive numbers ordered from smallest to largest.

## Output Arguments

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Result of interpolation, returned as an RF Toolbox network parameter object of the same type as `objnew`.

## Algorithms

The function uses the MATLAB function `interp1` to perform the interpolation operation. Overall performance is similar to the RF Toolbox `analyze` function. However, behaviors of the two functions differ when `freq` contains frequencies outside the range of the original data:

• `analyze` performs a zeroth-order extrapolation for out-of-range data points.

• `rfinterp1` inserts `NaN` values for out-of-range data points.