Suppose I have the following function
myFun <- function(formula, data){
f <- formula(formula)
dat <- model.frame(f, data)
dat
}
Applying it with this sample data yields a new dataframe:
qqq <- data.frame(grade = c(3, NA, 3,4,5,5,4,3), score = rnorm(8), idVar =
c(1:8))
dat <- myFun(score ~ grade, qqq)
However, what I would like is for the resulting dataframe (dat) to include as a
column idVar. Naively, I could do
dat <- myFun(score ~ grade + idVar, qqq)
This gives what I'm after in terms of the resulting data, but doesn't make
sense within the context of the model I am working on since idVar is not one of
the conditioning variables used, it has a different purpose altogether. So, I
was thinking another way is to attach it somehow afterwards. Something like:
myFun <- function(formula, data, id, na.action){
f <- formula(formula)
idVar <- data[, id]
dat <- model.frame(f, data, na.action = na.action)
dat[, id] <- idVar
dat
}
myFun(score ~ grade, qqq, id = 'idVar', na.action = NULL)
Of course, I intentionally use na.action = NULL here because the following
occurs, of course
> myFun(score ~ grade, qqq, id = 'idVar', na.action = na.omit)
Error in `[<-.data.frame`(`*tmp*`, , id, value = 1:8) :
replacement has 8 rows, data has 7
I see a few workarounds, but I am certain there is a cleaner way to accomplish
this.
Harold
> sessionInfo()
R version 2.9.0 (2009-04-17)
i386-pc-mingw32
locale:
LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
States.1252;LC_MONETARY=English_United
States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252
attached base packages:
[1] splines stats graphics grDevices utils datasets methods base
other attached packages:
[1] lme4_0.999375-28 Matrix_0.999375-25 lattice_0.17-22 xtable_1.5-5
adapt_1.0-4 MiscPsycho_1.4
[7] statmod_1.3.8
loaded via a namespace (and not attached):
[1] grid_2.9.0 tools_2.9.0
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