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Function Reference: chi2inv

statistics: x = chi2inv (p, df)

Inverse of the chi-squared cumulative distribution function (iCDF).

For each element of p, compute the quantile (the inverse of the CDF) of the chi-squared distribution with df degrees of freedom. The size of x is the common size of p and df. A scalar input functions as a constant matrix of the same size as the other inputs.

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

See also: chi2cdf, chi2pdf, chi2rnd, chi2stat

Source Code: chi2inv

Example: 1

  

 ## Plot various iCDFs from the chi-squared distribution
 p = 0.001:0.001:0.999;
 x1 = chi2inv (p, 1);
 x2 = chi2inv (p, 2);
 x3 = chi2inv (p, 3);
 x4 = chi2inv (p, 4);
 x5 = chi2inv (p, 6);
 x6 = chi2inv (p, 9);
 plot (p, x1, "-b", p, x2, "-g", p, x3, "-r", ...
       p, x4, "-c", p, x5, "-m", p, x6, "-y")
 grid on
 ylim ([0, 8])
 legend ({"df = 1", "df = 2", "df = 3", ...
          "df = 4", "df = 6", "df = 9"}, "location", "northwest")
 title ("Chi-squared iCDF")
 xlabel ("probability")
 ylabel ("values in x")
plotted figure