R help - Sep 2008 - How to update a column in a dataframe, more simply...

Hello,

I would like to be able to update an existing column in a dataframe, 
like this...

data$score[data$type=="1" &
data$year=="2001"]<-data$score * 0.111
data$score[data$type=="1" &
data$year=="2002"]<-data$score * 0.222
data$score[data$type=="1" &
data$year=="2003"]<-data$score * 0.333

...but, if possible, using simpler code. I've got several dozen lines of 
code like this (type 2, type3, etc. for the same years) so it would be 
great if I could reduce each set of three lines of code to one line

Any help much appreciated, thanks!

Mark

First of all, what you have will not work since you also have to
subset the RHS of the equation:

data$score[data$type=="1" &
data$year=="2001"]<-data$score[data$type=="1" &
data$year=="2001"] *
0.111

Another way is to construct a matrix of the values you want to search
for and change: (not tested)

change <- rbind(c(1, 2001, 0.111),
				c(1, 2002, 0.222),
				c(1, 2003, 0.333),
				c(2, 2001, 1.111),
				.....)
for (i in seq(nrow(change))){
	select <- data$type == change[i,1] & data$year == change[i,2]
	data$score[select] <- data$score[select] * change[i,3]
}



On Fri, Sep 26, 2008 at 6:35 PM, Mark Na <mtb954 at gmail.com>
wrote:
> Hello,
>
> I would like to be able to update an existing column in a dataframe, like
> this...
>
> data$score[data$type=="1" &
data$year=="2001"]<-data$score * 0.111
> data$score[data$type=="1" &
data$year=="2002"]<-data$score * 0.222
> data$score[data$type=="1" &
data$year=="2003"]<-data$score * 0.333
>
> ...but, if possible, using simpler code. I've got several dozen lines
of
> code like this (type 2, type3, etc. for the same years) so it would be
great
> if I could reduce each set of three lines of code to one line
>
> Any help much appreciated, thanks!
>
> Mark
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?