[R] Help with indexing

[jim holtman]

try this:

> # create a factor and then convert back to numeric
> x$nb <- as.integer(factor(x$name, levels=unique(x$name))) + 99
> x
  name freq  nb
1 Mary    1 100
2 Mary    2 100
3 Mary    3 100
4  Sam    1 101
5  Sam    2 101
6 John    1 102
7 John    2 102
8 John    3 102
9 John    4 102


On Sat, Nov 21, 2009 at 7:00 PM, Dana Sevak <dana.sevak at yahoo.com> wrote:
> Dear R Helpers,
>
> I am missing something very elementary here, and I don't seem to get it from the help pages of the ave, seq and seq_along functions, so I wonder if you could offer a quick help.
>
> To use an example from an earlier post on this list, I have a dataframe of this kind:
>
> dat = data.frame(name = rep(c("Mary", "Sam", "John"), c(3,2,4)))
> dat$freq = ave(seq_along(dat$name), dat$name, FUN = seq_along)
>
> dat
>  name freq
> 1 Mary    1
> 2 Mary    2
> 3 Mary    3
> 4  Sam    1
> 5  Sam    2
> 6 John    1
> 7 John    2
> 8 John    3
> 9 John    4
>
> What I need is another column assigning a number to each name starting from index 100, that is:
>
>  name freq  nb
> 1 Mary    1 100
> 2 Mary    2 100
> 3 Mary    3 100
> 4  Sam    1 101
> 5  Sam    2 101
> 6 John    1 102
> 7 John    2 102
> 8 John    3 102
> 9 John    4 102
>
> What is the easiest way to do this?
>
> Thanks a lot for your kind help.
>
> Dana
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?