I seem to have a Friday afternoon block and can't see the easiest way of doing this. Given a data frame like: dat <- data.frame(x = runif(100), y = runif(100), group = rep(letters[1:10], each = 10))> head(dat)x y group 1 0.876751503 0.6518345 a 2 0.627067150 0.8801790 a 3 0.632465192 0.1768305 a 4 0.060359554 0.8835652 a 5 0.675868776 0.7721177 a 6 0.008465241 0.5046486 a I want to work out cor(x, y) by group, so in this case ending up with 10 correlation coefficients by group. I'm not seeing a straightforward solution and I'd appreciate your help. Thanks David -- View this message in context: http://r.789695.n4.nabble.com/aggregation-type-question-tp4657966.html Sent from the R help mailing list archive at Nabble.com.
Hello,
With the following, the first instruction will give you correlations
matrices, the second coefficients.
dat <- read.table(text = "
x y group
1 0.876751503 0.6518345 a
2 0.627067150 0.8801790 a
3 0.632465192 0.1768305 a
4 0.060359554 0.8835652 a
5 0.675868776 0.7721177 a
6 0.008465241 0.5046486 a
", header = TRUE)
str(dat)
lapply(split(dat[, c("x", "y")], dat$group), cor)
lapply(split(dat[, c("x", "y")], dat$group), function(d)
cor(d$x, d$y))
Hope this helps,
Rui Barradas
Em 08-02-2013 16:33, carslaw escreveu:> I seem to have a Friday afternoon block and can't see the easiest way
of
> doing this.
>
> Given a data frame like:
>
> dat <- data.frame(x = runif(100), y = runif(100), group =
rep(letters[1:10],
> each = 10))
>> head(dat)
> x y group
> 1 0.876751503 0.6518345 a
> 2 0.627067150 0.8801790 a
> 3 0.632465192 0.1768305 a
> 4 0.060359554 0.8835652 a
> 5 0.675868776 0.7721177 a
> 6 0.008465241 0.5046486 a
>
> I want to work out cor(x, y) by group, so in this case ending up with 10
> correlation coefficients by group.
>
> I'm not seeing a straightforward solution and I'd appreciate your
help.
>
> Thanks
>
> David
>
>
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/aggregation-type-question-tp4657966.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
I seem to be suffering from the same problem (the Friday one, not the cor one) Have a look at http://stats.stackexchange.com/questions/4040/r-compute-correlation-by-group for something that looks like it will work John Kane Kingston ON Canada> -----Original Message----- > From: david.carslaw at kcl.ac.uk > Sent: Fri, 8 Feb 2013 08:33:45 -0800 (PST) > To: r-help at r-project.org > Subject: [R] aggregation-type question > > I seem to have a Friday afternoon block and can't see the easiest way of > doing this. > > Given a data frame like: > > dat <- data.frame(x = runif(100), y = runif(100), group > rep(letters[1:10], > each = 10)) >> head(dat) > x y group > 1 0.876751503 0.6518345 a > 2 0.627067150 0.8801790 a > 3 0.632465192 0.1768305 a > 4 0.060359554 0.8835652 a > 5 0.675868776 0.7721177 a > 6 0.008465241 0.5046486 a > > I want to work out cor(x, y) by group, so in this case ending up with 10 > correlation coefficients by group. > > I'm not seeing a straightforward solution and I'd appreciate your help. > > Thanks > > David > > > > -- > View this message in context: > http://r.789695.n4.nabble.com/aggregation-type-question-tp4657966.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.____________________________________________________________ FREE 3D EARTH SCREENSAVER - Watch the Earth right on your desktop!