Re: [R] Average every 4 columns

Uwe Ligges Wed, 09 Nov 2016 13:32:45 -0800


On 09.11.2016 22:06, Jim Lemon wrote:

Hi Milu,
Perhaps this will help:

apply(as.matrix(x[-1,seq(1:dim(x)[1],by=4)]),1,mean)


More efficient than apply(..., 1, mean): rowMeans()

Best,
Uwe Ligges


Jim


On Thu, Nov 10, 2016 at 4:00 AM, Miluji Sb <miluj...@gmail.com> wrote:

Thanks a lot for your quick reply. I made a mistake in the question, I
meant to ask every 4 (or 12) rows not columns. Apologies. Thanks again!

Sincerely,

Milu

On Wed, Nov 9, 2016 at 5:45 PM, Dalthorp, Daniel <ddalth...@usgs.gov> wrote:

Hi Milu,
The following should work for an array x (provided dim(x)[2] is divisible
by 4):

colMeans(x[,0:(dim(x)[2]/4-1)*4+1])

-Dan

On Wed, Nov 9, 2016 at 8:29 AM, Miluji Sb <miluj...@gmail.com> wrote:

Dear all,

I have a dataset with hundreds of columns, I am only providing only 12
columns. Is it possible to take the mean of every four (or 12) columns
 (value601, value602, value603, value604 etc.in this case) and repeat for
the hundreds of columns? Thank you.

Sincerely,

Milu

structure(list(value601 = c(10.1738710403442, 3.54112911224365,
12.9192342758179, 3.17447590827942, 11.7332258224487, 7.68282270431519,
-7.11564493179321, 0.987620949745178, 13.0476207733154, 6.36939525604248
), value602 = c(13.0642414093018, 5.53129482269287, 16.0519638061523,
2.88946437835693, 14.9204912185669, 9.42428588867188, -6.80674123764038,
-0.614241063594818, 16.7947769165039, 7.9541072845459), value603 =
c(22.0399188995361,
14.398024559021, 24.9523792266846, 12.0878629684448, 23.6459674835205,
18.3277816772461, -2.54092741012573, 10.5550804138184, 25.1016540527344,
16.2166938781738), value604 = c(27.7165412902832, 20.3255825042725,
30.8430004119873, 16.6856250762939, 29.2485408782959, 24.3775005340576,
6.47758340835571, 15.5897912979126, 30.7387924194336, 22.3637084960938
), value605 = c(31.6644763946533, 23.4093952178955, 35.1488723754883,
19.7132263183594, 33.3924179077148, 29.5846366882324, 10.2083873748779,
19.3551616668701, 35.3076629638672, 27.4299201965332), value606 =
c(33.9698333740234,
26.8574161529541, 36.8900833129883, 22.8604583740234, 34.8642921447754,
33.8158760070801, 14.7055835723877, 22.1144580841064, 37.0545425415039,
32.1087913513184), value607 = c(36.0279846191406, 26.9297180175781,
38.2701225280762, 23.2643146514893, 36.7398796081543, 34.1216125488281,
17.1387901306152, 24.0419750213623, 37.8542327880859, 32.7677421569824
), value608 = c(34.0242347717285, 25.7720966339111, 36.4897193908691,
22.0332260131836, 34.8011703491211, 32.6856842041016, 16.6232261657715,
21.5571365356445, 36.1491546630859, 31.1716938018799), value609 =
c(27.5402088165283,
21.7590408325195, 30.5214176177979, 18.4252090454102, 29.1156253814697,
26.9878330230713, 12.4962501525879, 17.7259578704834, 30.9099159240723,
25.4832077026367), value610 = c(23.4706859588623, 17.0126209259033,
26.8166942596436, 15.297459602356, 25.1733055114746, 23.5616931915283,
8.86995983123779, 13.5793552398682, 27.5732250213623, 22.1691932678223
), value611 = c(14.5820417404175, 9.08279132843018, 17.8419170379639,
8.36016654968262, 16.5633754730225, 14.8123331069946, 1.32095837593079,
5.73408317565918, 18.9752082824707, 13.5729999542236), value612 =
c(9.12979793548584,
2.79943537712097, 11.6504030227661, 2.21584677696228, 10.5404834747314,
7.55471754074097, -5.58141136169434, -0.566209673881531, 12.3264112472534,
6.65576601028442)), .Names = c("value601", "value602", "value603",
"value604", "value605", "value606", "value607", "value608", "value609",
"value610", "value611", "value612"), row.names = c("1", "2",
"3", "4", "5", "6", "7", "8", "9", "10"), class = "data.frame")

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--
Dan Dalthorp, PhD
USGS Forest and Rangeland Ecosystem Science Center
Forest Sciences Lab, Rm 189
3200 SW Jefferson Way
Corvallis, OR 97331
ph: 541-750-0953
ddalth...@usgs.gov


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and provide commented, minimal, self-contained, reproducible code.


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Re: [R] Average every 4 columns

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