regression - Julia contrast coding -


having trouble assigning custom contrasts categorical variables in regression. looks 1 can assign effectscoding or dummycoding using contrast parameter

    model = fit!(lmm(@formula(response ~ 1 + factor + (1|sub)), data,               contrasts = dict(:factor => effectscoding()) )) 

but how assign custom contrasts?

for instance, in r can do

contrasts(data$factor) <- cbind("a_vs_b"= c(0.5, -0.5, 0), "ab_vs_c"= c(-0.25, -0.25, 0.5))  > contrasts(data$factor)        a_vs_b   ab_vs_c        0.5     -0.25 b       -0.5     -0.25 c        0.0      0.50 

in addition effectscoding(), dataframes supports other contrast specifications. , in general, can supply contrast matrix (of right size, k-by-(k-1) k categories) in r. example:

using rdatasets        # install pkg.add("rdatasets") using mixedmodels      # install pkg.add("mixedmodels")  iris = dataset("datasets", "iris")  contrast_matrix = [0.5 -0.25; -0.5 -0.25; 0.0 0.5] fit!(lmm(@formula(sepallength ~ 1 + species + (1|petalwidth)), iris,    contrasts = dict(:species => contrastscoding(contrast_matrix)) )) 

the specific contrast matrix in question helmert coding matrix ordering of categories. in case, simpler do:

fit!(lmm(@formula(sepallength ~ 1 + species + (1|petalwidth)), iris,    contrasts = dict(:species => helmertcoding()) )) 

helmertcoding takes optional arguments base , levels (not named, see docs) switch around category orderings.

hope helps, actual code gave few problems on v0.7 julia, on v0.5 should work.


Comments

Popular posts from this blog

python Tkinter Capturing keyboard events save as one single string -

android - InAppBilling registering BroadcastReceiver in AndroidManifest -

javascript - Z-index in d3.js -