Question

I have a tab delimited file like

A   B   0.5
A   C   0.75
B   D   0.2

And I want to convert it to a square matrix, like

       A      B      C       D
A      0     0.5    0.75     0
B             0      0      0.2 
C                    0       0
D                            0

How can I go about it in R?
Thanks,

Answer 1

If you have the data in a data frame with the following column names:

Var1    Var2    value

you can use

xtabs(value ~ Var1 + Var2, data = df)

See the plyr package for some more general data reshaping functions also.