[R] aggregation-type question

[John Kane]

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
> 
> 
> 
> --
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