Hi
r-help-bounces at r-project.org napsal dne 19.04.2011 09:46:47:
Dear R Users,
Lets assume I have this data frame:
x y z
1 1.00 5 0.5
2 1.02 5 0.7
3 1.04 7 0.1
4 1.06 9 0.4
x and y columns are sorted and the values not necessarily integers. z
values are not sorted. Now I would like to create a matrix out of this
with x as first column values and y as first row values. Matrix element
a_11 shall be left NA. The a_ij should have the z value for the
corresponding x and y pair. The result shall be some sort of a grid and
then e.g. look like:
[,1] [,2] [,3] [,4] [,5]
[1,] NA 5 6 7 9 (y)
[2,] 1.00 0.5 NA NA NA
[3,] 1.02 0.7 NA NA NA
[4,] 1.04 NA NA 0.1 NA
[5,] 1.06 NA NA NA 0.4
(x)
This example is just for illustration. The resulting matrix should have
more numeric values than NA's.
I am not sure if this is the solution you want
tab<-xtabs(z~x+y, data=df)
tab[tab==0]<-NA