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convert data frame of values into correlation matrix

3 messages · Juliet Hannah, David Winsemius, Gabor Grothendieck

Juliet Hannah
# 
Hi Group,

Consider a data frame like this:

mylabel1 <- rep(c("A","B","C"),each=3)
mylabel2 <- rep(c("A","B","C"),3)
corrs <- c(1,.8,.7,.8,1,.7,.7,.7,1)
 myData <- data.frame(mylabel1,mylabel2,corrs)

myData

  mylabel1 mylabel2 corrs
1        A        A   1.0
2        A        B   0.8
3        A        C   0.7
4        B        A   0.8
5        B        B   1.0
6        B        C   0.7
7        C        A   0.7
8        C        B   0.7
9        C        C   1.0

I would like to find a general way to get this matrix from the above dataframe.

corrmat <- matrix(corrs,nrow=3,byrow=TRUE)
row.names(corrmat) <- c("A","B","C")
colnames(corrmat) <- c("A","B","C")
corrmat
    A   B   C
A 1.0 0.8 0.7
B 0.8 1.0 0.7
C 0.7 0.7 1.0

The solution I have is the one above where I rearrange the data so
that I can just use matrix() on one
of the columns. I am looking for a solution in which I don't have to do this.

Thanks,

Juliet
David Winsemius
#
On Jan 30, 2010, at 2:11 PM, Juliet Hannah wrote:

            

      
      
      
    

        
Possibilities:

 >> reshape(myData, timevar="mylabel2", direction="wide",  
v.names="corrs", idvar="mylabel1")[,2:4]
   corrs.A corrs.B corrs.C
1     1.0     0.8     0.7
4     0.8     1.0     0.7
7     0.7     0.7     1.0
#---------
 > unstack(myData, corrs ~ mylabel2 )
     A   B   C
1 1.0 0.8 0.7
2 0.8 1.0 0.7
3 0.7 0.7 1.0
#-------
library(reshape)
mdat <- melt(myData)
cast(mdat, mylabel1 ~ mylabel2 )

   mylabel1   A   B   C
1        A 1.0 0.8 0.7
2        B 0.8 1.0 0.7
3        C 0.7 0.7 1.0


-- .

David Winsemius, MD
Heritage Laboratories
West Hartford, CT

  
  


  


      

    

    

      
      

        


  

        

      Gabor Grothendieck
    

    

      
      #
    

  


  

      
Try his:

xtabs(corrs ~., myData)

        
On Sat, Jan 30, 2010 at 2:11 PM, Juliet Hannah <juliet.hannah at gmail.com> wrote: