chi2cdf (Statistics Toolbox)

Chi-square (²) cumulative distribution function (cdf)

Syntax

```
P = chi2cdf(X,V)
```

Description

P = chi2cdf(X,V) computes the ² cdf at each of the values in X using the corresponding parameters in V. Vector or matrix inputs for X and V must have the same size. A scalar input is expanded to a constant matrix with the same dimensions as the other input. The degrees of freedom parameters in V must be positive integers, and the values in X must lie on the interval [0 1].

The ² cdf for a given value x and degrees-of-freedom is

where ( · ) is the Gamma function. The result, p, is the probability that a single observation from a ² distribution with degrees of freedom will fall in the interval [0 x].

The ² density function with degrees-of-freedom is the same as the gamma density function with parameters /2 and 2.

Examples

probability = chi2cdf(5,1:5)
probability =
    0.9747    0.9179    0.8282    0.7127    0.5841
probability = chi2cdf(1:5,1:5)
probability =
    0.6827    0.6321    0.6084    0.5940    0.5841

cdfplot chi2inv