sapply to automate doing a series ofparallel analyses

["Hunsicker, Lawrence" <lawrence-hunsicker@uiowa.edu>]

So here I am back to the trough for help.  You guys are really teaching me how to program S-Plus, and I appreciate the help.

So I now have a function named testScrMiss, which does a mixed model logistic regression to test which other values in a data set predict whether a serum creatinine determination was obtained.  (You all know the function from my last messages.)

The function now works fine, with a single integer parameter indexing the specific column that I want to test.  I’d now like to run this function on a long list of columns – indexed by c(5:7,11:12,15:16,20,27:29,32:33,38:42,45,50,55:64,72,77:93,99:100,107) to be specific.  So I try:

list1 <- c(5:7,11:12,15:16,20,27:29,32:33,38:42,45,50,55:64,72,77:93,99:100,107)

sapply(list1, testScrMiss)

Aaarrrrgghh!  I get the following error:

Problem in FUN(...X.sub.i....): Length of x (variable 2) is 5 != length of others (24151)

Use traceback() to see the call stack

So I use traceback to see if I can figure out why S-Plus thinks that some variable is length 5.  This turns out to be the number of columns in my original data.frame that I reference in the function – the dependent and independent variable in the fixed formula and the three nested levels in the random formula. 

Now if I run a familiar function like sqrt (remembering that I have a column of integer indices),

list1 <- c(5:7,11:12,15:16,20,27:29,32:33,38:42,45,50,55:64,72,77:93,99:100,107)

sapply(list1, sqrt)

I get the expected outcome – a list of the square roots of my original list. 

Now I am suspecting that the latter works because the function sqrt is polymorphic, with different functions for a single integer and for a list of integers.  But I have been flailing around, trying lots of different ways to get this thing to work, and I have not succeeded yet.  So I am again asking for help.

Meanwhile I am going back to Tim Hesterbereg’s comments on scoping problems to see I can understand what is going on.

Again, thanks to all for your repeated help.

Larry Hunsicker