manuelreif / pp Goto Github PK

in the manual entry for PP_4pl, how is beta_i defined in terms of thres? for a partial credit model, I'm confused as to why the first row must be zeros.

To Reproduce
Run the example code in the PPall documentation, substituting the following code for the awmatrix variable:

# Just one person instead of five... awmatrix will be [1,1:6] instead of [1:5,1:6]
awmatrix <- matrix(c(1,0,1,0,1,1
                  # ,1,0,0,1,2,0
                  # ,0,0,0,0,0,0
                  # ,0,1,1,2,2,1
                  # ,1,1,1,0,0,1
                  ),byrow=TRUE,ncol=6)

# This call will fail when awmatrix has only one row
respmixed_mle <- PPall(respm = awmatrix,thres = THRESx, 
                     slopes = sl,lowerA = la, upperA=ua,type = "mle",
                     model2est=model2est)

The error message is Error in NR_mixed(...) : Not a matrix

To Fix
The problem appears to be on PP/PPall.R, line 172:
respm <- respm[!is.na(resPPx[,2]),]

When respm is an integer matrix with only one row, this line converts respm to an integer vector. drop=FALSE needs to be added to prevent the conversion.