MATLAB Function Reference
std

Standard deviation

Syntax

• ```s = std(X)
s = std(X,flag)
s = std(X,flag,dim)
```

Definition

There are two common textbook definitions for the standard deviation `s` of a data vector `X`.

where

and is the number of elements in the sample. The two forms of the equation differ only in versus in the divisor.

Description

```s = std(X), ``` where `X` is a vector, returns the standard deviation using (1) above. If `X` is a random sample of data from a normal distribution, is the best unbiased estimate of its variance.

If `X` is a matrix, `std(X)` returns a row vector containing the standard deviation of the elements of each column of `X`. If `X` is a multidimensional array, `std(X)` is the standard deviation of th elements along the first nonsingleton dimension of `X`.

```s = std(X,flag) ``` for `flag = 0,` is the same as `std(X)`. For `flag = 1`, `std(X,1)` returns the standard deviation using (2) above, producing the second moment of the sample about its mean.

```s = std(X,flag,dim) ``` computes the standard deviations along the dimension of `X` specified by scalar `dim`.

Examples

For matrix `X`

• ```X =
1     5     9
7    15    22
s = std(X,0,1)
s =
4.2426    7.0711    9.1924
s = std(X,0,2)
s =
4.000
7.5056
```

`corrcoef`, `cov`, `mean`, `median`