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summary of problem with mCall function.
2 messages · Bill Shipley, Douglas Bates
2 days later
On 9/7/05, Bill Shipley <bill.shipley at usherbrooke.ca> wrote:
Last week I posted a question concerning the mCall function, which is used to create self-starting functions and is described in the book by Pinheiro, J.C. and Bates, D.M. (Mixed-effects models in S and S-PLUS). On page 345 one finds the following call: xy<-sortedXyData(mCall[["x"]], LHS,data) It is necessary to replace the "x" in the call to mCall by the actual variable name for the dependent variable. The error message that I was getting was due to the fact that I had called by dependent variable in the data frame (data) by another name than x without changing this in the call to mCall.
mCall isn't a function. It's a matched call created by the match.call function. The purpose of having such a matched call is to be able to map the actual arguments to the formal arguments. You need to know which names to evaluate in the data frame and you can only get that information from the matched call.