Statistics: chi2cdf

### Function Reference: `chi2cdf`

statistics: p = chi2cdf (x, df)
statistics: p = chi2cdf (x, df, `"upper"`)

Chi-squared cumulative distribution function (CDF).

For each element of x, compute the cumulative distribution function (CDF) of the chi-squared distribution with df degrees of freedom. The chi-squared density function with df degrees of freedom is the same as a gamma density function with parameters `df/2` and `2`.

The size of p is the common size of x and df. A scalar input functions as a constant matrix of the same size as the other input.

`p = chi2cdf (x, df, "upper")` computes the upper tail probability of the chi-squared distribution with df degrees of freedom, at the values in x.

Further information about the chi-squared distribution can be found at https://en.wikipedia.org/wiki/Chi-squared_distribution

See also: chi2inv, chi2pdf, chi2rnd, chi2stat

Source Code: chi2cdf

### Example: 1

     ## Plot various CDFs from the chi-squared distribution
     x = 0:0.01:8;
     p1 = chi2cdf (x, 1);
     p2 = chi2cdf (x, 2);
     p3 = chi2cdf (x, 3);
     p4 = chi2cdf (x, 4);
     p5 = chi2cdf (x, 6);
     p6 = chi2cdf (x, 9);
     plot (x, p1, "-b", x, p2, "-g", x, p3, "-r", ...
           x, p4, "-c", x, p5, "-m", x, p6, "-y")
     grid on
     xlim ([0, 8])
     legend ({"df = 1", "df = 2", "df = 3", ...
              "df = 4", "df = 6", "df = 9"}, "location", "southeast")
     title ("Chi-squared CDF")
     xlabel ("values in x")
     ylabel ("probability")