#polychoric

download GSL

install GSL by './configure && make && sudo make install'

gem install gsl

gem install statsample

gem install statsample-bivariate-extension

Afterwards, let's try some toy examples. I am interest in polychoric correlation between two variables/raters.

calculate the polychoric correlation of the following cross table:

------------------- | y=0 | y=1 | y=2 | ------------------- x = 0 | 1 | 10 | 20 | ------------------- x = 1 | 20 | 20 | 50 | -------------------

matrix=Matrix[[1,10,20],[20,20,50]] poly=Statsample::Bivariate::Polychoric.new(matrix, :method=>:joint) puts poly.r

or

poly=Statsample::Bivariate::Polychoric.new_with_vectors([1,10,20].to_scale, [20,20,50].to_scale) puts poly.r

Replace Polychoric with Tetrachoric if your data is dichotomous instead of ordinal.