[R] Take the maximum of every 12 columns

Tue Feb 20 16:38:45 CET 2018

Don't do this (sorry Thierry)! max() already does this -- see ?max

> x <- data.frame(a =rnorm(10), b = rnorm(10))
> max(x)
[1] 1.799644

> max(sapply(x,max))
[1] 1.799644

Cheers,
Bert

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Tue, Feb 20, 2018 at 7:05 AM, Thierry Onkelinx <thierry.onkelinx at inbo.be>
wrote:

> The maximum over twelve columns is the maximum of the twelve maxima of
> each of the columns.
>
> single_col_max <- apply(x, 2, max)
> twelve_col_max <- apply(
>   matrix(single_col_max, nrow = 12),
>   2,
>   max
> )
>
> ir. Thierry Onkelinx
> Statisticus / Statistician
>
> Vlaamse Overheid / Government of Flanders
> INSTITUUT VOOR NATUUR- EN BOSONDERZOEK / RESEARCH INSTITUTE FOR NATURE
> AND FOREST
> Team Biometrie & Kwaliteitszorg / Team Biometrics & Quality Assurance
> thierry.onkelinx at inbo.be
> Havenlaan 88 bus 73, 1000 Brussel
> www.inbo.be
>
> ////////////////////////////////////////////////////////////
> ///////////////////////////////
> To call in the statistician after the experiment is done may be no
> more than asking him to perform a post-mortem examination: he may be
> able to say what the experiment died of. ~ Sir Ronald Aylmer Fisher
> The plural of anecdote is not data. ~ Roger Brinner
> The combination of some data and an aching desire for an answer does
> not ensure that a reasonable answer can be extracted from a given body
> of data. ~ John Tukey
> ////////////////////////////////////////////////////////////
> ///////////////////////////////
>
>
>
>
> 2018-02-20 15:55 GMT+01:00 Miluji Sb <milujisb at gmail.com>:
> >  Dear all,
> >
> > I have monthly data in wide format, I am only providing data (at the
> bottom
> > of the email) for the first 24 columns but I have 2880 columns in total.
> >
> > I would like to take max of every 12 columns. I have taken the mean of
> > every 12 columns with the following code:
> >
> > byapply <- function(x, by, fun, ...)
> > {
> >   # Create index list
> >   if (length(by) == 1)
> >   {
> >     nc <- ncol(x)
> >     split.index <- rep(1:ceiling(nc / by), each = by, length.out = nc)
> >   } else # 'by' is a vector of groups
> >   {
> >     nc <- length(by)
> >     split.index <- by
> >   }
> >   index.list <- split(seq(from = 1, to = nc), split.index)
> >
> >   # Pass index list to fun using sapply() and return object
> >   sapply(index.list, function(i)
> >   {
> >     do.call(fun, list(x[, i], ...))
> >   })
> > }
> >
> > ## Compute annual means
> > y <- byapply(df, 12, rowMeans)
> >
> > How can I switch rowMeans with a command that takes the maximum? I am a
> bit
> > baffled. Any help will be appreciated. Thank you.
> >
> > Sincerely,
> >
> > Milu
> >
> > ###
> > dput(droplevels(head(x, 5)))
> > structure(list(X0 = c(295.812103271484, 297.672424316406,
> 299.006805419922,
> > 297.631500244141, 298.372741699219), X1 = c(295.361328125,
> > 297.345092773438,
> > 298.067504882812, 297.285339355469, 298.275268554688), X2 =
> > c(294.279602050781,
> > 296.401550292969, 296.777984619141, 296.089111328125, 297.540374755859
> > ), X3 = c(292.103118896484, 294.253601074219, 293.773803710938,
> > 293.916229248047, 296.129943847656), X4 = c(288.525024414062,
> > 291.274505615234, 289.502777099609, 290.723388671875, 293.615112304688
> > ), X5 = c(286.018371582031, 288.748565673828, 286.463134765625,
> > 288.393951416016, 291.710266113281), X6 = c(285.550537109375,
> > 288.159149169922, 285.976501464844, 287.999816894531, 291.228271484375
> > ), X7 = c(289.136962890625, 290.751159667969, 290.170257568359,
> > 291.796203613281, 293.423248291016), X8 = c(292.410003662109,
> > 292.701263427734, 294.25244140625, 295.320404052734, 295.248199462891
> > ), X9 = c(293.821655273438, 294.139068603516, 296.630157470703,
> > 296.963531494141, 296.036224365234), X10 = c(294.532531738281,
> > 295.366607666016, 297.677551269531, 296.715911865234, 296.564178466797
> > ), X11 = c(295.869476318359, 297.010070800781, 299.330169677734,
> > 297.627593994141, 297.964935302734), X12 = c(295.986236572266,
> > 297.675567626953, 299.056671142578, 297.598907470703, 298.481842041016
> > ), X13 = c(295.947601318359, 297.934448242188, 298.745391845703,
> > 297.704925537109, 298.819091796875), X14 = c(294.654327392578,
> > 296.722717285156, 297.0986328125, 296.508239746094, 297.822021484375
> > ), X15 = c(292.176361083984, 294.49658203125, 293.888305664062,
> > 294.172149658203, 296.117095947266), X16 = c(288.400726318359,
> > 291.029113769531, 289.361907958984, 290.566772460938, 293.554016113281
> > ), X17 = c(285.665222167969, 288.293029785156, 286.118957519531,
> > 288.105285644531, 291.429382324219), X18 = c(285.971252441406,
> > 288.3798828125, 286.444580078125, 288.495880126953, 291.447326660156
> > ), X19 = c(288.79296875, 290.357543945312, 289.657928466797,
> > 291.449066162109, 293.095275878906), X20 = c(291.999877929688,
> > 292.838348388672, 293.840362548828, 294.412322998047, 294.941253662109
> > ), X21 = c(293.615447998047, 294.028106689453, 296.072296142578,
> > 296.447387695312, 295.824615478516), X22 = c(294.719848632812,
> > 295.392028808594, 297.453216552734, 297.114288330078, 296.883209228516
> > ), X23 = c(295.634429931641, 296.783294677734, 298.592346191406,
> > 297.469512939453, 297.832122802734)), .Names = c("X0", "X1",
> > "X2", "X3", "X4", "X5", "X6", "X7", "X8", "X9", "X10", "X11",
> > "X12", "X13", "X14", "X15", "X16", "X17", "X18", "X19", "X20",
> > "X21", "X22", "X23"), row.names = c(NA, 5L), class = "data.frame")
> >
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> >
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> ______________________________________________
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> posting-guide.html
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