R help - Jan 2010 - convert data frame of values into correlation matrix

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

On Jan 30, 2010, at 2:11 PM, Juliet Hannah wrote:
> 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.
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

Try his:

xtabs(corrs ~., myData)


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