[R] [External] converting MATLAB -> R | element-wise operation

[Evan Cooch]

Very interesting - thanks! Most of my problems are not limited by 
compute speed, but its clear that for some sorts of compute-intensive 
problems, sweep might be a limiting approach.

On 2/29/2024 6:12 PM, Richard M. Heiberger wrote:
> I decided to do a direct comparison of transpose and sweep.
>
>
> library(microbenchmark)
>
> NN <- matrix(c(1, 2, 3, 4, 5, 6), nrow = 2, byrow = TRUE)  # Example matrix
> lambda <- c(2, 3, 4)  # Example vector
> colNN <- t(NN)
>
> microbenchmark(
>    sweep     = sweep(NN, 2, lambda, "/"),
>    transpose = t(t(NN)/lambda),
>    colNN     = colNN/lambda
> )
>
>
> Unit: nanoseconds
>        expr   min    lq     mean median      uq   max neval cld
>       sweep 13817 14145 15115.06  14350 14657.5 75932   100 a
>   transpose  1845  1927  2151.68   2132  2214.0  7093   100  b
>       colNN    82   123   141.86    123   164.0   492   100   c
>
> Note that transpose is much faster than sweep because it is doing less work,
> I believe essentially just changing the order of indexing.
>
> Using the natural sequencing for column-ordered matrices is much much faster.
>
>> On Feb 28, 2024, at 18:43, peter dalgaard<pdalgd using gmail.com>  wrote:
>>
>>> rbind(1:3,4:6)/t(matrix(c(2,3,4), 3,2))
>

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