[R] Conditional Correlation

[Daniel Malter]

This question was just answered yesterday in this post:
http://r.789695.n4.nabble.com/Correlations-by-subgroups-td3599548.html#a3600553

One solution:

x<-c(1,1,1,1,1,2,2,2,2,2) 
y<-rnorm(10) 
z<-y+rnorm(10) 
by(data.frame(y,z),factor(x),cor) 

HTH,
Daniel



Mateus Rabello wrote:
> 
> Hi, 
> How can I accomplish this in R. Example:  
> 
> I have the following data.frame:
> 
> data <-
> data.frame(x=c(1,2,3,4,5,6,5,3,7,1,0,4,8),y=c(1,2,1,2,2,2,1,1,1,2,2,2,2),z=c(5,8,4,3,4,1,6,3,3,6,3,5,7))
> 
> Supposing that data$y is a factor, I would like to find the Spearman
> correlation between data$x and data$z indexing it by data$y. 
> To be more specific, I want to find two correlations: between x and z with
> y==1 and the same correlation with x and z where y==2.
> Something like:
> 
> cor(data$x[data$y==1],data$z[data$y==1],method= "spearman") and
> cor(data$x[data$y==2],data$z[data$y==2],method= "spearman"),
> 
> but without having to write all the values for data$y and use cor more
> than once.
> 
> I hope I made myself clear.
> Thanks
> Mateus
> 
> 
> 	[[alternative HTML version deleted]]
> 
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