[R] Using apply

[Peter Langfelder]

It should be said that for many basic statistics, there are faster
functions than apply, for example here you want

sum = colSums(x)

As already said, for sum of squares you would do colSums(x^2).

Many useful functions of this kind are implemented in package
matrixStats. Once you install it, either look at the package manual or
type ls("package:matrixStats") to see a list of functions. Most if not
all have self-explanatory names.

HTH,

Peter
On Tue, Oct 30, 2018 at 7:28 PM Steven Yen <styen using ntu.edu.tw> wrote:
>
> I need help with "apply". Below, I have no problem getting the column sums.
> 1. How do I get the sum of squares?
> 2. In general, where do I look up these functions?
> Thanks.
>
> x<-matrix(1:10,nrow=5); x
> sum <- apply(x,2,sum); sum
>
>
>
>
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