On Apr 2, 2010, at 10:36 AM, Steve Murray wrote:
Dear all,
Thanks for the contributions so far. I've had a look at these and
the closest I've come to solving it is the following:
data_ave <- ave(data$rammday, by=c(data$month, data$year))
Warning messages:
1: In split.default(x, g) :
data length is not a multiple of split variable
2: In split.default(seq_along(x), f, drop = drop, ...) :
data length is not a multiple of split variable
I'm slightly confused by the warning message, as the data lengths do
appear the same:
dim(data)
[1] 1073 6
length(data$year)
[1] 1073
length(data$month)
[1] 1073
All, true no doubt, but did you look at
length (c(data$month, data$year) ) # ??
--
David.
Maybe the approach I'm taking is wrong. Any suggestions would be
gratefully received.
Many thanks,
Steve
----------------------------------------
Date: Wed, 31 Mar 2010 23:31:25 +0200
From: stephan.kola...@gmx.de
To: smurray...@hotmail.com
CC: r-help@r-project.org
Subject: Re: [R] Summing data based on certain conditions
?by may also be helpful.
Stephan
Steve Murray schrieb:
Dear all,
I have a dataset of 1073 rows, the first 15 which look as follows:
data[1:15,]
date year month day rammday thmmday
1 3/8/1988 1988 3 8 1.43 0.94
2 3/15/1988 1988 3 15 2.86 0.66
3 3/22/1988 1988 3 22 5.06 3.43
4 3/29/1988 1988 3 29 18.76 10.93
5 4/5/1988 1988 4 5 4.49 2.70
6 4/12/1988 1988 4 12 8.57 4.59
7 4/16/1988 1988 4 16 31.18 22.18
8 4/19/1988 1988 4 19 19.67 12.33
9 4/26/1988 1988 4 26 3.14 1.79
10 5/3/1988 1988 5 3 11.51 6.33
11 5/10/1988 1988 5 10 5.64 2.89
12 5/17/1988 1988 5 17 37.46 20.89
13 5/24/1988 1988 5 24 9.86 9.81
14 5/31/1988 1988 5 31 13.00 8.63
15 6/7/1988 1988 6 7 0.43 0.00
I am looking for a way by which I can create monthly totals of
rammday (rainfall in mm/day; column 5) by doing the following:
For each case where the month value and the year are the same
(e.g. 3 and 1988, in the first four rows), find the mean of the
the corresponding rammday values and then times by the number of
days in that month (i.e. 31 in this case).
Note however that the number of month values in each case isn't
always the same (e.g. in this subset of data, there are 4 values
for month 3, 5 for month 4 and 5 for month 5). Also the months
will of course recycle for the following years, so it's not simply
a case of finding a monthly total for *all* the 3s in the whole
dataset, just those associated with each year in turn.
How would I go about doing this in R?
Any help will be gratefully received.
Many thanks,
Steve
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