On Jun 1, 2012, at 2:37 PM, Sarah Goslee wrote:
There are several ways. The easiest to understand is probably using
if() statements: see ?if for help and examples.
Sarah
I would have thought ifelse() to be the necessary function, but for
such simple cases I find boolean math to be clearer. (I understand
indivdiual preferences vary in this area.)
> dft <-data.frame(Y=1, M=sample(c(1,3,9),20,repl=TRUE))
> dft$res <- with(dft, Y*( (M==1) *1 + (M==3)*2 +(M==9)*3.6678) )
> dft
Y M res
1 1 1 1.0000
2 1 9 3.6678
3 1 3 2.0000
4 1 1 1.0000
5 1 1 1.0000
6 1 9 3.6678
7 1 9 3.6678
8 1 9 3.6678
9 1 3 2.0000
10 1 9 3.6678
11 1 9 3.6678
12 1 9 3.6678
13 1 1 1.0000
14 1 3 2.0000
15 1 3 2.0000
16 1 1 1.0000
17 1 1 1.0000
18 1 3 2.0000
19 1 9 3.6678
20 1 9 3.6678
--
David
On Fri, Jun 1, 2012 at 11:34 AM, jfca283 <jfca...@gmail.com> wrote:
Hi
I need to do something very simple. I have 2 variables, Y and M. I
need to
multiply Y by 1 if M=1, by 2 if M=3 and by 3.6678 if M=9. How do i
make it?
Thanks for your time and interest
--
David Winsemius, MD
West Hartford, CT
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