[R] how to generate a column based on other columns in a data frame

[Gabor Grothendieck]

Assuming this data frame:
DF <- data.frame(X = c(36.435, 36.435, 36.435, 35.329, 35.329,
36.431, 36.431, 35.421, 35.421, 35.421), Y = c(30.118, 30.118,
30.118, 29.657, 29.657, 30.111, 30.111, 29.797, 29.797, 29.797))

# Try this:
DF$site <- as.numeric(factor(interaction(DF$X, DF$Y)))

If X and Y can vary slightly while still referring to the same
site then round them first to k decimal places first.  See ?round


On Feb 11, 2008 11:30 AM, Weidong Gu <wgu at uab.edu> wrote:
> HI,
>
>
>
> I am working on a data set with multiple collections of mosquitoes at
> sampling sites. Each row represents a collection of individual samples
> with coordinates for each collection.
>
> ... X,  Y,...
>
> 1  36.435 30.118
>
> 2  36.435 30.118
>
> 3  36.435 30.118
>
> 4  35.329 29.657
>
> 5  35.329 29.657
>
> 6  36.431 30.111
>
> 7  36.431 30.111
>
> 8  35.421 29.797
>
> 9  35.421 29.797
>
> 10 35.421 29.797
>
>
>
> Unfortunately, there is no 'site' entry. I would like to add a column of
> 'site' based on the coordinates of samples so that samples from the same
> sites have the same site ID like S1, S2,....
>
>
>
> How to do this in R way? Thanks.
>
>
>
>
>
> Weidong Gu,
>
> Department of Medicine
> University of Alabama, Birmingham
> 1900 University Blvd., Birmingham, Alabama 35294
> Email: wgu at uab.edu
> PH: (205)-975-9053
>
>
>
>
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>
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