[R] simple if statement

[Philipp Pagel]

On Fri, Apr 07, 2006 at 02:58:00AM -0400, Brian Quinif wrote:
> 
> I have data on college students.  I want to make a string variable
> that has the names of the years.  That is, when the year variable i is
> equal to 1, I want to have a variable called years equal to
> "Freshmen".
> 
> I tried this
> years <- "Freshmen" if i==1
> years <- "Sophomores" if i==2

What you are looking for is not an if clause but logical indexing:

years[years=="Freshmen"] <- 1
years[years=="Sophomores"] <- 2

Of course it's still a character vector so you will have to do

years = as.numeric(years)

Have a look at the manual (Introduciotn to R) for more details.

Another question is what you have in mind. To me it looks like what you
are trying to do is make a factor on your own. Maybe this is what you
want:

factor(years)

or maybe

factor(years, levels=c("Freshmen", "Sophomores"))

if you want more control over the coding.

cu
	Philipp

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