[R] Converting unique strings to unique numbers

[Kate Ignatius]

I have a pedigree file as so:

X0001 BYX859      0      0  2  1 BYX859
X0001 BYX894      0      0  1  1 BYX894
X0001 BYX862 BYX894 BYX859  2  2 BYX862
X0001 BYX863 BYX894 BYX859  2  2 BYX863
X0001 BYX864 BYX894 BYX859  2  2 BYX864
X0001 BYX865 BYX894 BYX859  2  2 BYX865

And I was hoping to change all unique string values to numbers.

That is:

BYX859 = 1
BYX894 = 2
BYX862 = 3
BYX863 = 4
BYX864 = 5
BYX865 = 6

But only in columns 2 - 4.  Essentially I would like the data to look like this:

X0001 1 0 0  2  1 BYX859
X0001 2 0 0  1  1 BYX894
X0001 3 2 1  2  2 BYX862
X0001 4 2 1  2  2 BYX863
X0001 5 2 1  2  2 BYX864
X0001 6 2 1  2  2 BYX865

Is this possible with factors?

Thanks!

K.