[R] help on replacing values

[Gabor Grothendieck]

Your columns are factors, not character strings.  Use as.is = TRUE as
an argument to read.table.   Also its a bit dangerous to use T although
not wrong.  Its safer to use TRUE.

On 9/7/07, darteta001 at ikasle.ehu.es <darteta001 at ikasle.ehu.es> wrote:
> Dear List,
>
> I have a newbie question. I have read in a data.frame as follows:
>
> > data = read.table("table.txt", header = T)
> > data
>  X1 X2 X3 X4
> A AB AC AB AC
> B AB AC AA AB
> C AA AB AA AB
> D AA AB AB AC
> E AB AA AA AB
> F AB AA AB AC
> B AB AC AB AA
>
> I would like to replace AA values by BB in column X2. I have tried
> using replace() with no success, although I am not sure this is the
> right function. This is the code I have used:
>
> data$X2 <- replace(data$X2, data$X2 =="AA","BB")
> Warning message:
> invalid factor level, NAs generated in: `[<-.factor`(`*tmp*`, list,
> value = "BB")
>
> What is wrong with the code? How can I get this done? how about
> changing AA values by BB in all 4 columns simultaneously? Actually
> this is a small example dataframe, the real one would have about 1000
> columns.
>
> Extendind this, I found a similar thread dated July 2006 that used
> replace() on iris dataset, but I have tried reproducing it obtaining
> same warning message
>
>  iris$Species <- replace(iris$Species, iris$Species
> == "setosa","NewName")
> Warning message:
> invalid factor level, NAs generated in: `[<-.factor`(`*tmp*`, list,
> value = "NewName")
>
> Thanks in advance your help,
>
> David
>
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