See ?pmax for getting the max for each year.
do.call('pmax', oil[-1])
Or equivalently:
pmax(oil$TX, oil$CA, oil$AL, oil$ND)
apply and which.max will give you the index:
i <- apply(oil[-1], 1, which.max)
which you can use to extract the state:
names(oil[-1])[i]
Jason
-----Original Message-----
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
Behalf Of Tim Umbach
Sent: Thursday, October 17, 2013 9:49 AM
To: r-help@r-project.org
Subject: [R] Selecting maximums between different variables
Hi there,
another beginners question, I'm afraid. Basically i want to selct the maximum
of values, that correspond to different variables. I have a table of oil
production that looks somewhat like this:
oil <- data.frame( YEAR = c(2011, 2012),
TX = c(20000, 30000),
CA = c(40000, 25000),
AL = c(20000,
21000),
ND = c(21000,60000))
Now I want to find out, which state produced most oil in a given year. I tried
this:
attach(oil)
last_year = oil[ c(YEAR == 2012), ]
max(last_year)
Which works, but it doesnt't give me the corresponding values (i.e. it just
gives me the maximum output, not what state its from).
So I tried this:
oil[c(oil == max(last_year)),]
and this:
oil[c(last_year == max(last_year)),]
and this:
oil[which.max(last_year),]
and this:
last_year[max(last_year),]
None of them work, but they don't give error messages either, the output is
just "NA". The problem is, in my eyes, that I'm comparing the values of
different variables with each other. Because if i change the structure of the
dataframe (which I can't do with the real data, at least not with out doing it
by hand with a huge dataset), it looks like this and works
perfectly:
oil2 <- data.frame (
names = c('YEAR', 'TX', 'CA', 'AL', 'ND'),
oil_2011 = c(2011, 20000, 40000, 20000, 21000),
oil_2012 = c(2012, 30000, 25000, 21000, 60000)
)
attach(oil2)
oil2[c(oil_2012 == max(oil_2012)),]
Any help is much appreciated.
Thanks, Tim Umbach
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