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Matrix max by row

Wacek Kusnierczyk
Rolf Turner wrote:
hmm, since i was called by name (i'm grateful, rolf), i feel obliged to
check the matters myself:

    # dummy data, presumably a 'large matrix'?
    n = 5e3
    m = matrix(rnorm(n^2), n, n)

    # what is to be benchmarked...
    waku = expression(matrix(apply(m, 1, max), nrow(m)))
    bert = expression(do.call(pmax,data.frame(m)))

    # to be benchmarked
    library(rbenchmark)
    benchmark(replications=10, order='elapsed', columns=c('test',
'elapsed'),
       waku=matrix(apply(m, 1, max), nrow(m)),
       bert=do.call(pmax,data.frame(m)))

takes quite a while, but here you go:

    #   test elapsed
    # 1 waku  11.838
    # 2 bert  20.833

where bert's solution seems to require a wonder to 'be considerably
faster for large matrices'.  to have it fair, i also did

    # to be benchmarked
    library(rbenchmark)
    benchmark(replications=10, order='elapsed', columns=c('test',
'elapsed'),
       bert=do.call(pmax,data.frame(m)),
       waku=matrix(apply(m, 1, max), nrow(m)))

    #  test elapsed
    # 2 waku  11.695
    # 1 bert  20.912
   
take home point: a good product sells itself, a bad product may not sell
despite aggressive marketing.

rolf, thanks for pointing this out.

cheers,
vQ

Thread (9 messages)

Ana M Aparicio Carrasco Matrix max by row Mar 28 Wacek Kusnierczyk Matrix max by row Mar 28 jim holtman Matrix max by row Mar 28 Bert Gunter Matrix max by row Mar 29 Rolf Turner Matrix max by row Mar 29 Bill Venables Matrix max by row Mar 29 Wacek Kusnierczyk Matrix max by row Mar 30 Bert Gunter Matrix max by row Mar 30 Wacek Kusnierczyk Matrix max by row Mar 30