Alexander Schwall
2011-Aug-12 18:27 UTC
[R] testEquatingData (part of ltm package) changes order of columns
Dear R community, I hope someone is out there who has some insights into the ltm package. Specifically, I am seeking help for the testEquatingData function which is part of this package. Here is an example of my data: #install.packages("ltm", dependencies = TRUE) library(ltm) anchor<- as.data.frame(cbind(c(NA, NA, NA, NA, 1), c(NA, NA, NA, 1, NA), c(1,1,NA,NA,NA))) names(anchor) <- c("A1","A2", "A3") items <- list(as.data.frame(cbind(c(NA, NA, NA, NA, 1), c(NA, NA, NA, 1, NA), c(1,1,NA,NA,NA)))) #let's assume these are the items that I want to estimate datAll <- testEquatingData(items, AnchoringItems = anchor) Now, after I run the testEquatingData() function, the order of the variables has been changed to A3, V3, A1, A2, V1, V2, instead of, for example A1, A2, A3, V1, V2,V3, or V1, V2, V3, A1, A2, A3. Since I am using the constraint function of the three parameter estimation function [e.g. tpm(datAll, contraint) I would like Anchor items not to be interspersed with the items to be estimated (V1, V2, etc). I can arrange the order of my constraint parameters to match the order of the anchor items, but also including regular items gets tricky. Of particular concern is that second part of the datAll list (which can be seen when running datAll). The stars indicate that an item is an anchoring items. However, Their order does not match the order of the actual items. I hope this makes sense. Any help would be appreciated. Thanks, Alexander [[alternative HTML version deleted]]