[R] Difficulty with LRSM Rasch analysis with eRm package in R.

Nicholas Commons-Miller ncommons at gmail.com
Fri Apr 15 17:34:25 CEST 2016


I am trying to do an LRSM Rasch analysis for 72-item data. 67 of the 
items are binary, and 5 are ternary. I have tried it with and without a 
specified matrix, and cannot get it to work.

The primary problems I am having are:
1. Without a matrix, I get an error:

Error in `rownames<-`(`*tmp*`, value = betanames) : length of 'dimnames' 
[1] not equal to array extent

This is from these commands:
rGrps = c(rep.int(1, nrow(X)))
results.LRSM <- LRSM(X, mpoints = 1, groupvec = rGrps, se = TRUE)

2. I don't know how to make a design matrix myself. I tried making one 
with 1's along the diagonal, but it doesn't seem to work. I get an error:

Error in likLR(X, W, mpoints, groupvec, model, st.err = se, sum0, 
etaStart) : Mismatch between number of rows (beta's) in W and number of 
items (categories) in X!

This is from these commands:
rGrps = c(rep.int(1, nrow(X)))
W = matrix(data=NA, nrow=ncol(X), ncol=ncol(X))
for(i in 1:(ncol(X) - 8))
   vec = c(rep(0, i - 1),1,rep(0, (ncol(X) - i)))
   W[i,] = vec
results.LRSM <- LRSM(X, W, mpoints = 1, groupvec = rGrps, se = TRUE)

Both of these errors seem to arise somewhere within the eRm code, and I 
have had great difficulty finding specifically where. I am using R 
Studio, but I do not seem to be able to figure out the debugging, 
particularly when I need it to go into eRm package files.

So basically, if I could get a few points of help, I would appreciate it:
1. How do I create a design matrix?
2. Why do the betas seem to not match the data? (The betanames to the 
rownames, or the betas to categories.)
3. How do I use R Studio debugging to step into the package files?

Thank you,
Nicholas Commons-Miller

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