Hi. Here is one approach:
x <- rep(c("A", "B", "C"), c(3,1,2))
DF <- data.frame(x, stringsAsFactors=FALSE)
cbind(DF, new_c=c(lapply(rle(DF$x)[[1]], function(x) 1:x), recursive=T))
Andrija
On Wed, May 28, 2014 at 10:46 PM, Marcos Santos <mmsantos...@gmail.com>wrote:
> I have a "data frame" like this:
>
> Category Observed_value A 100 A 130 A 140 B 90 C 80 D 120 D 130
>
> I need to create an index column that show the number of the observation
> for each category. I have three observations in the category A, one in
> category B, one in category C and two in category D. The new matrix should
> be like this:
>
>
> Category Observed_value Index A 100 1 A 130 2 A 140 3 B 90 1 C 80 1
> D 120 1 D 130 2
>
> Please, could anyone help me with this problem?
>
> Thank you.
> --
> Marcos Martins Santos
> mmsantos...@gmail.com
> --
> Skype: marcosmartinssantos
>
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>
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>
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