This should get you close:

> x <- read.table(textConnection("st  vc  y
+ A   Z   .2
+ B   Z   .4
+ B   Y   .3
+ C   Y   .1
+ C   X   .8"), header=TRUE)
> closeAllConnections()
>
> x
  st vc   y
1  A  Z 0.2
2  B  Z 0.4
3  B  Y 0.3
4  C  Y 0.1
5  C  X 0.8
> x.1 <- melt(x)
Using st, vc as id variables
> x.1
  st vc variable value
1  A  Z        y   0.2
2  B  Z        y   0.4
3  B  Y        y   0.3
4  C  Y        y   0.1
5  C  X        y   0.8
> cast(x.1, st ~ vc)
  st   X   Y   Z
1  A  NA  NA 0.2
2  B  NA 0.3 0.4
3  C 0.8 0.1  NA
>


On Mon, Apr 26, 2010 at 10:35 AM, Robin Jeffries <rjeffries@ucla.edu> wrote:

> I do get the following error message:
>
> *Error in lookup.svc[i, j] <- svc[svc$st == unique(svc$st)[i] & svc$vc ==
>  : *
> *  replacement has length zero*
>
>
> I also thought it might be because of how R treats NA, but then I would
> expect the loop to stop at the place of error (i=1, j=2) and not continue
> to
> fill out all of column i.
>
> I've tried using %in%, but that seems to do a non-positional check for
> whether or not entries are *somewhere *in those vectors. I need to find the
> location of where the match occurs.
>
> My goal is to turn this:
>
> st  vc  y
> A   Z   .2
> B   Z   .4
> B   Y   .3
> C   Y   .1
> C   X   .8
>
> into a 2x2 table with entries 'y'
>           vc
>        Z   Y   X
>     A  .2  0   0
> st   B  .4  .3  0
>     C  0   .1  .8
>
>
> Right now it's giving me
>
>           vc
>        Z   Y   X
>     A  .2  0.000   0.000
> st   B  0  0  0
>     C  0   0  0
>
> So it seems to finish out the row that it's currently on, but then won't
> continue to loop.
>
>
> -Robin
>
>
>
> On Sun, Apr 25, 2010 at 4:44 PM, Peter Alspach <
> Peter.Alspach@plantandfood.co.nz> wrote:
>
> > Tena koe Robin
> >
> > Do you get an error or warning?
> >
> > It may have something to do with how == treats NA:
> >
> > x <- 1:4
> > x[x == 1]
> > [1] 1
> > x <- c(1:4, NA)
> > x[x == 1]
> > [1]  1 NA
> > x[x %in% 1]
> > [1] 1
> >
> > If so, using %in% is one way to avoid the problem.  However, I would
> > have thought you'd get an error message if this were the case.
> >
> > HTH .....
> >
> > Peter Alspach
> >
> > > -----Original Message-----
> > > From: r-help-bounces@r-project.org [mailto:r-help-bounces@r-
> > > project.org] On Behalf Of Robin Jeffries
> > > Sent: Monday, 26 April 2010 10:26 a.m.
> > > To: r-help@r-project.org
> > > Subject: [R] Obvious reason for not looping twice?
> > >
> > > Is there an obvious reason why this won't loop to i=2 and beyond?
> > > There are many combinations of *st* & *vc* that don't exist in svc.
> > For
> > > example, when s=1 there's only an entry at v=1.  That's fine, the
> > entry
> > > can
> > > stay 0.
> > >
> > > lookup.svc <-
> > > array(0,dim=c(length(unique(svc$st)),length(unique(svc$vc))),
> > > dimnames=list(unique(svc$st), unique(svc$vc)))
> > >
> > > for (i in 1:length(unique(svc$st))) {
> > >   for (j in 1:length(unique(svc$vc))){
> > >      lookup.svc[i,j] <- svc[svc$st == unique(svc$st)[i] & svc$vc ==
> > > unique(svc$vc)[j], 4]
> > > }}
> > >
> > >
> > > Thanks,
> > > Robin
> > >
> > > ~~~~~~~~~~~~~~~~~~~
> > > -Robin Jeffries
> > > Dr.P.H. Candidate
> > > UCLA School of Public Health
> > > rjeffries@ucla.edu
> > > 530-624-0428
> > >
> > >       [[alternative HTML version deleted]]
> > >
> > > ______________________________________________
> > > R-help@r-project.org mailing list
> > > https://stat.ethz.ch/mailman/listinfo/r-help
> > > PLEASE do read the posting guide http://www.R-project.org/posting-<http://www.r-project.org/posting->
> > > guide.html
> > > and provide commented, minimal, self-contained, reproducible code.
> >
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

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