how to deduplicate records, e.g. using melt() and cast()

Esteemed UseRs,

This must be embarrassingly trivial to achieve with e.g., melt() and 
cast(): deduplicating records ("pw.X" in example) for a given set of 
responses ("cond.Y" in example).

Hopefully the runnable example shows clearly what i have and what i'm 
trying to convert it to. But i'm just not getting it, ?cast that is! So 
i'd really appreciate some ones patience to clarify this, using the 
reshape package, or any other approach.

With sincere thanks in advance,

Karl


## Runnable example
## The data.frame i have:
library("reshape")
my.df <- data.frame(pathway = c(rep("pw.A", 2), rep("pw.B", 3), 
rep("pw.C", 1)),
                    cond.one = c(0.5, NA, 0.4, NA, NA, NA),
                    cond.two = c(NA, 0.6, NA, 0.9, NA, 0.2),
                    cond.three = c(NA, NA, NA, NA, 0.1, NA))
my.df
## The data fram i want:
wanted.df  <- data.frame(pathway = c("pw.A", "pw.B", "pw.C"),
                    cond.one = c(0.5, 0.4, NA),
                    cond.two = c(0.6, 0.9, 0.2),
                    cond.three = c(NA, 0.1, NA))
wanted.df

Karl Brand
Dept of Cardiology and Dept of Bioinformatics
Erasmus MC
Dr Molewaterplein 50
3015 GE Rotterdam
T +31 (0)10 703 2460 |M +31 (0)642 777 268 |F +31 (0)10 704 4161