# [R] factor as seq() in for loop

Spencer Graves spencer.graves at pdf.com
Wed Sep 21 16:31:22 CEST 2005

```	  Does the follow help?

> aFactor <- factor(rep(letters[1:3], 1:3))
> aFactor
[1] a b b c c c
Levels: a b c
> for(af in levels(aFactor)){
+   print(sum(aFactor==af))
+ }
[1] 1
[1] 2
[1] 3

spencer graves

Tord Snall wrote:

> Dear all,
> I would like to use the values in vegaggr.BLMCMR02\$colony
>
> str(vegaggr.BLMCMR02)
> `data.frame':   1678 obs. of  3 variables:
> \$ vegtype       : Factor w/ 27 levels "2010","2020",..: 3 4 5 19 4 5 19 5
> \$ colony        : Factor w/ 406 levels "0","1","10","100",..: 1 1 1 1 2 2 2
> \$ Totvegproparea: num  0.00055 0.03956 0.95705 0.00284 0.05215 ...
>
> as the seq in a for loop (for(var in seq)), and therefore first picked them
> out as
> cols = aggregate(list(A = vegaggr.BLMCMR02\$Totvegproparea),
>                 list(colony = vegaggr.BLMCMR02\$colony), sum)[,1]
>
>>str(cols)
>
>  Factor w/ 406 levels "0","1","10","100",..: 1 2 3 4 5 6 7 8 9 10 ...
>
> I next planned to transform cols using as.integer(cols). However, this
> transformation gives a vector corresponding to seq(from=1,to=length(cols)).
>
> Could someone please give advice on how to make use of a factor as the seq
> in a for loop (which is strictly not allowed' according to ?Control).
>
> Thanks!
>
> Tord
>
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--
Spencer Graves, PhD
Senior Development Engineer
PDF Solutions, Inc.
333 West San Carlos Street Suite 700
San Jose, CA 95110, USA

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