CHC Theory, Cognitive Assessment, R

Interactive 3D Multidimensional Scaling of the WJ III

I have been playing around with interactive 3D images (with the rgl package in R) and thought that it would be fun to present a multidimensional scaling (MDS) of the WJ III NU. Kevin McGrew has produced a number of beautiful images with MDS. My favorite is this one, not just because it is gorgeous, but because of the theoretical insights it communicates.

I simply took the correlation matrix from the WJ III NU standardization sample (ages 9 to 13) and subtracted each correlation from 1 to produce a distance measure. I performed classic MDS in R with the cmdscale function, allowing 3 dimensions. I colored each test with my guess as to which CHC factor it belongs.

If you click the static image below, you can play with it (Firefox and Chrome worked for me but Internet Explorer and Safari did not.):

WJ III MDS in 3D

WJ III MDS in 3D

R code used to generate this image

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