| Detailed description |
The empirical ICC draws the points representing the relative frequencies shifted by one unit if the data set contains no zero scores. Example:
library(eRm)
x0 = sim.rasch(2000,8)
m0 = RM(x0)
plotICC(m0,empICC=list("raw")) # perfect plot
x1 = x0[rowSums(x0)>0,]
m1 = RM(x1)
plotICC(m1,empICC=list("raw")) # shifted by 1 unit
The bug may be associated with lines 117-118 of plotICC.Rm():
rel.freq <- freq.table[, 2]/rowSums(freq.table)
idx <- as.numeric(rownames(freq.table))
I want to thank Davide Albers for pointing me at the bug.
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