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stats::covariance

Covariance of data samples

Use only in the MuPAD Notebook Interface.

This functionality does not run in MATLAB.

Syntax

stats::covariance([x1, x2, …], [y1, y2, …], <Sample | Population>)
stats::covariance([[x1, y1], [x2, y2], …], <Sample | Population>)
stats::covariance(s, <c1, c2>, <Sample | Population>)
stats::covariance(s, <[c1, c2]>, <Sample | Population>)
stats::covariance(s1, <c1>, s2, <c2>, <Sample | Population>)

Description

stats::covariance([x1, x2, …, xn], [y1, y2, …, yn]) returns the covariance

,

where and are the arithmetic means of the data xi and yi, respectively.

stats::covariance([x1, x2, …, xn], [y1, y2, …, yn], Population) returns

.

If the input data are floating-point numbers, the sums defining the covariance are computed in a numerically stable way. If a floating point result is desired, it is recommended to make sure that all input data are floats.

For exact input data, exact symbolic expressions are returned.

The column indices c1, c2 are optional if the data are given by a stats::sample object s containing only two non-string data columns. If the data are provided by two samples s1, s2, the column indices are optional for samples containing only one non-string data column.

External statistical data stored in an ASCII file can be imported into a MuPAD® session via import::readdata. In particular, see Example 1 of the corresponding help page.

Examples

Example 1

We compute the covariance of samples passed as lists:

X := [2, 33/7, 21/9, PI]: Y :=  [3, 5, 1, 7]:
stats::covariance(X, Y)

Alternatively, the data may be passed as a list of data pairs:

stats::covariance([[2, 3], [33/7, 5], [21/9, 1], [PI, 7]])

If all data are floating-point numbers, the result is a float:

stats::covariance(float(X), float(Y))

delete X, Y:

Example 2

We create a sample of type stats::sample:

s := stats::sample([[1.0, 2.4, 3.0],
                    [7.0, 4.8, 4.0],
                    [3.3, 3.0, 5.0]])
1.0  2.4  3.0
7.0  4.8  4.0
3.3  3.0  5.0

We compute the covariance of the first column and the third column in several equivalent ways:

stats::covariance(s, 1, 3),
stats::covariance(s, [1, 3]),
stats::covariance(s, 1, s, 3)

delete s:

Example 3

The covariance of symbolic data is returned as a symbolic expression:

stats::covariance([x1, x2], [y1, y2])

expand(%)

Parameters

x1, y1, x2, y2, …

The statistical data: arithmetical expressions. The number of data xi must coincide with the number of data yi.

s, s1, s2

Samples of type stats::sample

c1, c2

Column indices: positive integers. Column c1 of s or s1, respectively, provides the data xi. Column c2 of s or s2, respectively, provides the data yi.

Options

Sample

The data are regarded as a "sample", not as a full population. This is the default.

Population

The data are regarded as the whole population, not as a sample.

See Also

MuPAD Functions

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