[R] for loop, error in model frame.default ... variable lengths differ

Peter Keller kellerp.l at gmail.com
Mon May 21 04:10:57 CEST 2012


I'm failing to get a for loop working.  I'm sure it's something simple, and I
have found some posts relating to it, but I'm just not understanding why
this isn't working. 

I have a data frame and would like to loop through specific column names,
using aggregate() within a for loop.  There are NA's scattered throughout
the data frame and I'm thinking it has something to do with that, but I
haven't been able to fix it.

vars <- colnames(df)[c(10,12,16,18,20,21,24:29,45)]
 for(i in 1:length(vars)) {
    aggregate(colnames(df)[i] ~ x1 + x2 + x3, df, mean,
na.action=na.exclude)
    }

I get this error: 
Error in model.frame.default(formula = colnames(df)[i] ~ x1 + x2 +   : 
  variable lengths differ (found for 'x1')

There are probably much better ways to do this, and I would be happy to get
suggestions, but mostly I would like to know why the code isn't working.

Thanks-
Peter

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