[R] apply with a division

[Gabor Grothendieck]

This should work whether your data, x, is a data frame or a matrix:

x / x[rep(1, nrow(x)),]


On Thu, Jul 3, 2008 at 6:04 PM, Greg Kettler <gkettler at gmail.com> wrote:
> Hi,
> I'd like to normalize a dataset by dividing each row by the first row.
> Very simple, right?
> I tried this:
>
>> expt.fluor
>  X1  X2  X3
> 1 124 120 134
> 2 165 163 174
> 3  52  51  43
> 4 179 171 166
> 5 239 238 235
>
>>first.row <- expt.fluor[1,]
>> normed <- apply(expt.fluor, 1, function(r) {r / first.row})
>>normed
> [[1]]
>  X1 X2 X3
> 1  1  1  1
>
> [[2]]
>        X1       X2       X3
> 1 1.330645 1.358333 1.298507
>
> [[3]]
>         X1    X2        X3
> 1 0.4193548 0.425 0.3208955
>
> [[4]]
>        X1    X2       X3
> 1 1.443548 1.425 1.238806
>
> [[5]]
>        X1       X2       X3
> 1 1.927419 1.983333 1.753731
>
> Ugly! The values are right, but why didn't I get another 2D array
> back? Shouldn't the division in my inline function return a vector?
>
> Thanks,
> Greg
>
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