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

[Petr PIKAL]

Hi

r-help-bounces at r-project.org napsal dne 06.04.2011 22:02:29:

>   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 $25,000
>    if ((hh.sub$HHFAMINC[indx] == '06') | (hh.sub$HHFAMINC[indx] == '07') 

> | (hh.sub$HHFAMINC[indx] == '08') | (hh.sub$HHFAMINC[indx] == '09') | 
> (hh.sub$HHFAMINC[indx] == '10'))
>      hh.sub$CS_FAMINC[indx] <- 2 # $25,000 to $50,000
>    if ((hh.sub$HHFAMINC[indx] == '11') | (hh.sub$HHFAMINC[indx] == '12') 

> | (hh.sub$HHFAMINC[indx] == '13') | (hh.sub$HHFAMINC[indx] == '14') | 
> (hh.sub$HHFAMINC[indx] == '15'))
>      hh.sub$CS_FAMINC[indx] <- 3 # $50,000 to $75,000
>    if ((hh.sub$HHFAMINC[indx] == '16') | (hh.sub$HHFAMINC[indx] == 
'17'))
>      hh.sub$CS_FAMINC[indx] <- 4 # $75,000 to $100,000
>    if ((hh.sub$HHFAMINC[indx] == '18'))
>      hh.sub$CS_FAMINC[indx] <- 5 # More than $100,000
>    if ((hh.sub$HHFAMINC[indx] == '-7') | (hh.sub$HHFAMINC[indx] == '-8') 

> | (hh.sub$HHFAMINC[indx] == '-9'))
>      hh.sub$CS_FAMINC[indx] = 0
> }

Take advantage of factors. If hh.sub$HHFAMINC was factor you can recode it 
by

levels(hh.sub$HHFAMINC)<-appropriate vector of new levels with the same 
length as levels

Something like

> x<-factor(letters[1:5])
> x
[1] a b c d e
Levels: a b c d e
> levels(x)<-c(1,1,2,2,1)
> x
[1] 1 1 2 2 1
Levels: 1 2
>

Regards
Petr



> 
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