The task today was to find what variables had significant relations with an important grouping variable in the big dataset I’ve been working with lately. The grouping variable has 3 levels, and represents different behaviours of interest. At first I tried putting the grouping variable as a dependent variable in a multinomial logistic regression, but I didn’t really trust the output, and the goal was really just to construct a bunch of graphs showing significant bivariate nominal relations in the data..
That’s when I turned to my good old friend, the chi squared test. All I had to do was select all the variables that I wanted to test against the grouping variable, and construct a list of the chi squared statistic from each test, the variable being tested, and the crosstab of the two variables for later graphing. So that’s exactly what I did:
One really sweet thing about matrices in R is that you can mix them up with some parts having just numbers, some parts having text, and sub-matrices in other parts! A typical row of the “resultlist” would look something like this:
xsq testvar xtab
[1,] 200.7 “variable1″ numeric,6
Then all I needed to do to see the variable name and crosstab for that variable was to call “resultlist[1,2:3]”, and that gave me the numbers to graph.