[R] reshaping data.frame question

[Matthias Braeunig]

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Dear R-helpers,

my data.frame is of the form

x <- data.frame( f=gl(4,3), X=rep(0:2,4), p=c(.1,.2,.3))
x
   f X   p
1  1 0 0.1
2  1 1 0.2
3  1 2 0.3
4  2 0 0.1
5  2 1 0.2
6  2 2 0.3
7  3 0 0.1
8  3 1 0.2
9  3 2 0.3
10 4 0 0.1
11 4 1 0.2
12 4 2 0.3

which  tabulates some values p(X) for several factors f.

Now I want to put it in "wide" format, so that factor levels appear as
column heads. Note also that X starts from zero. It would be nice if I
could simply access p_f[X==0] as f[0]. How can I possibly do that?

(The resilting object does not have to be a data.frame. As there are
only numeric values, also a matrix would do.)

I tried the following

y<-unstack(x,form=p~f)
row.names(y) <- 0:2
y
   X1  X2  X3  X4
0 0.1 0.1 0.1 0.1
1 0.2 0.2 0.2 0.2
2 0.3 0.3 0.3 0.3

Now, how to access X3[0], say?

Maybe reshape would be the right tool, but I could not figure it out.

I appreciate your help. Thanks!


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