[R] to print system.time always

[Uwe Ligges]

On 03.11.2012 16:52, mrzung wrote:
> Hi all;
>
> I want to print system.time whenever I execute any command.
>
> It takes too much time to type "system.time()" function to all command.
>
> is there any solution on it?

See ?Rprof on how to profile your code.

>
> And,
>
> apply(matrix,1,cumsum) command is too slow to some large matrix.
>
> is there any function like rowCumSums ?

You had:

result1 <- apply(matrix,1,cumsum)


This is only "slow", if you have lots of rows. Now "think in matrices" 
how to to that:

b <- sapply(1:ncol(matrix), function(i) c(rep(1, i), rep(0, ncol(matrix)-i)
result2 <- t(x %*% b)

This is roughly 10 times faster on a 1000000 x 10 matrix.

Check the results:
all.equal(result1, result2)


Uwe Ligges






> thank u!
>
>
>
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