Statistics: gampdf

### Function Reference: `gampdf`

statistics: y = gampdf (x, k, theta)

Gamma probability density function (PDF).

For each element of x, compute the probability density function (PDF) of the Gamma distribution with shape parameter k and scale parameter theta. The size of y is the common size of x, k and theta. A scalar input functions as a constant matrix of the same size as the other inputs.

There are two equivalent parameterizations in common use:

1. With a shape parameter k and a scale parameter θ, which is used by `gampdf`.
2. With a shape parameter α = k and an inverse scale parameter β = 1 / θ, called a rate parameter.

Further information about the Gamma distribution can be found at https://en.wikipedia.org/wiki/Gamma_distribution

See also: gamcdf, gaminv, gamrnd, gamfit, gamlike, gamstat

Source Code: gampdf

### Example: 1

     ## Plot various PDFs from the Gamma distribution
     x = 0:0.01:20;
     y1 = gampdf (x, 1, 2);
     y2 = gampdf (x, 2, 2);
     y3 = gampdf (x, 3, 2);
     y4 = gampdf (x, 5, 1);
     y5 = gampdf (x, 9, 0.5);
     y6 = gampdf (x, 7.5, 1);
     y7 = gampdf (x, 0.5, 1);
     plot (x, y1, "-r", x, y2, "-g", x, y3, "-y", x, y4, "-m", ...
           x, y5, "-k", x, y6, "-b", x, y7, "-c")
     grid on
     ylim ([0,0.5])
     legend ({"α = 1, θ = 2", "α = 2, θ = 2", "α = 3, θ = 2", ...
              "α = 5, θ = 1", "α = 9, θ = 0.5", "α = 7.5, θ = 1", ...
              "α = 0.5, θ = 1"}, "location", "northeast")
     title ("Gamma PDF")
     xlabel ("values in x")
     ylabel ("density")