[R] Need a more efficient way to implement this type of logic in R

[Duncan Murdoch]

On 06/04/2011 4:02 PM, Walter Anderson wrote:
>    I have cobbled together the following logic.  It works but is very
> slow.  I'm sure that there must be a better r-specific way to implement
> this kind of thing, but have been unable to find/understand one.  Any
> help would be appreciated.
>
> hh.sub<- households[c("HOUSEID","HHFAMINC")]
> for (indx in 1:length(hh.sub$HOUSEID)) {
>     if ((hh.sub$HHFAMINC[indx] == '01') | (hh.sub$HHFAMINC[indx] == '02')
> | (hh.sub$HHFAMINC[indx] == '03') | (hh.sub$HHFAMINC[indx] == '04') |
> (hh.sub$HHFAMINC[indx] == '05'))
>       hh.sub$CS_FAMINC[indx]<- 1 # Less than $25,000

The answer is to think in terms of vectors and logical indexing.  The 
code above is equivalent to

hh.sub$CS_FAMINC[ hh.sub$HHFAMINC %in% c('01', '02', '03', '04', '05') ] 
<- 1

I've left off the rest of the loop, but I think it's similar.

Duncan Murdoch