# [R] change values in data frames

jim holtman jholtman at gmail.com
Sat Jun 28 05:17:49 CEST 2008

```Is this what you want:

> x
cola colb
1    1    c
2    1    i
3    1    i
4    1    c
5    2    i
6    2    c
7    2    c
8    2    i
9    2    i
> # generate run lengths
> z <- rle(x\$colb)
> # calculate offset of each starting sequence
> offsets <- head(cumsum(c(1, z\$lengths)), -1)
> # now determine where the 'i' is more than 1
> long <- which(z\$lengths > 1 & z\$values == 'i')
> # now replace all 'i' with 'I'
> x\$colb[x\$colb == 'i'] <- 'I'
> # replace lon runs with 'h'
> for (i in long){
+     x\$colb[(offsets[i]+1):(offsets[i] + z\$lengths[i] - 1)] <-
rep('h', z\$lengths[i] - 1)
+ }
> x
cola colb
1    1    c
2    1    I
3    1    h
4    1    c
5    2    I
6    2    c
7    2    c
8    2    I
9    2    h
>
>

On Fri, Jun 27, 2008 at 5:17 AM, poul <morteterre at infonie.fr> wrote:
>
> Hello every body,
> I am quite a new user of R so I beg your pardon for this naive question and
> the lake of syntax with wich I ask it:
>
> I have a data frames like this:
>
> cola    colb
> 1       c
> 1       i
> 1       i
> 1       c
> 2       i
> 2       c
> 2       c
> 2       i
> 2       i
> ...
> 10000
>
> I would like ,for each level of cola and for x in colb:
>
> -if colb[x]=="i" and colb[x-1] does not exist (first row in dataframes),
> then replace colb[x] by "l"
> -if colb[x]=="i" and colb[x-1]=="c" (previous row in data frmes), then
> replace colb[x] by "l"
> -if colb[x]=="i" and colb[x-1]=="i" (previous row in data frmes), then
> replace colb[x] by "h"
>
>
> Paul
>
> --
> View this message in context: http://www.nabble.com/change-values-in-data-frames-tp18151205p18151205.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> and provide commented, minimal, self-contained, reproducible code.
>

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

What is the problem you are trying to solve?

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