[R] Summary information by groups programming assitance
Søren Højsgaard
Soren.Hojsgaard at agrsci.dk
Mon Dec 22 23:25:46 CET 2008
Maybe summaryBy (or lapplyBy/splitBy) in the doBy package might help you.
Regards
Søren
________________________________
Fra: r-help-bounces at r-project.org på vegne af Ranney, Steven
Sendt: ma 22-12-2008 22:51
Til: r-help at r-project.org
Emne: [R] Summary information by groups programming assitance
All -
I have data that looks like
psd Species Lake Length Weight St.weight Wr
Wr.1 vol
432 substock SMB Clear 150 41.00 0.01 95.12438
95.10118 0.0105
433 substock SMB Clear 152 39.00 0.01 86.72916
86.70692 0.0105
434 substock SMB Clear 152 40.00 3.11 88.95298
82.03689 3.2655
435 substock SMB Clear 159 48.00 0.04 92.42095
92.34393 0.0420
436 substock SMB Clear 159 48.00 0.01 92.42095
92.40170 0.0105
437 substock SMB Clear 165 47.00 0.03 80.38023
80.32892 0.0315
438 substock SMB Clear 171 62.00 0.21 94.58105
94.26070 0.2205
439 substock SMB Clear 178 70.00 0.01 93.91912
93.90571 0.0105
440 substock SMB Clear 179 76.00 1.38 100.15760
98.33895 1.4490
441 S-Q SMB Clear 180 75.00 0.01 97.09330
97.08035 0.0105
442 S-Q SMB Clear 180 92.00 0.02 119.10111
119.07522 0.0210
...
[truncated]
where psd and lake are categorical variables, with five and four
categories, respectively. I'd like to find the maximum vol and the
lengths associated with each maximum vol by each category by each lake.
In other words, I'd like to have a data frame that looks something like
Lake Category Length vol
Clear substock 152 3.2655
Clear S-Q 266 11.73
Clear Q-P 330 14.89
...
Pickerel substock 170 3.4965
Pickerel S-Q 248 10.69
Pickerel Q-P 335 25.62
Pickerel P-M 415 32.62
Pickerel M-T 442 17.25
In order to originally get this, I used
with(smb[Lake=="Clear",], tapply(vol, list(Length, psd),max))
with(smb[Lake=="Enemy.Swim",], tapply(vol, list(Length, psd),max))
with(smb[Lake=="Pickerel",], tapply(vol, list(Length, psd),max))
with(smb[Lake=="Roy",], tapply(vol, list(Length, psd),max))
and pulled the values I needed out by hand and put them into a .csv.
Unfortunately, I've got a number of other data sets upon which I'll need
to do the same analysis. Finding a programmable alternative would
provide a much easier (and likely less error prone) method to achieve
the same results. Ideally, the "Length" and "vol" data would be in a
data frame such that I could then analyze with nls.
Does anyone have any thoughts as to how I might accomplish this?
Thanks in advance,
Steven Ranney
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