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

[Richard M. Heiberger]

I added two more rows

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)
matlam <- matrix(lambda, byrow=TRUE, nrow=2, ncol=3)

microbenchmark(
  sweep     = sweep(NN, 2, lambda, "/"),
  transpose = t(t(NN)/lambda),
  colNN     = colNN/lambda,
  fullsize  = NN / matrix(lambda, byrow=TRUE, nrow=2, ncol=3),
  rowlam  = NN / matlam
)

Unit: nanoseconds
      expr   min    lq     mean  median      uq   max neval cld
     sweep 12546 12792 13919.91 12997.0 13325.0 85608   100 a
 transpose  1640  1763  1986.04  1947.5  2050.0  7462   100  b
     colNN    82    82   161.13   123.0   123.0  3854   100   c
  fullsize   738   820   932.34   881.5   963.5  2829   100  bc
    rowlam    82   123   168.92   164.0   164.0   820   100   c

reshaping the denominator to the correct size in advance is very helpful if you will be doing this division more than once.



> On Feb 29, 2024, at 18:12, Richard M. Heiberger <rmh using temple.edu> 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))
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.r-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.