On Aug 20, 2011, at 12:32 PM, Uwe Ligges wrote:
On 20.08.2011 17:04, Wendy wrote:
Hi all,
I have a data.frame like following
A<-c('d0','d0','d1','d1','d2','d2')
B<-rep(c('control','sample'),3)
C<-c(rep(100000,2),200,300,400,500)
dataframe<-data.frame(A,B,C)
I want to reshape the matrix, so the matrix with 'd0', 'd1' and
'd2' in rows
and 'control' and 'sample' in columns. Is there a function for
doing this
easily?
See ?reshape
reshape(data=dataframe, idvar="A", timevar="B", direction="wide")
Uwe Ligges
Many people have experienced problems understanding the mechanics of
the base function 'reshape'. If you do not and if do continue to use
it, you would be doing the world a great service by writing a tutorial
manual with a bunch of worked examples. I have never found a tutorial
that clarified how I should use it in the variety of situations where
I have needed it.
So Hadley wrote an alternate facility ... the reshape package that
does not have a reshape function in it but rather two functions 'melt'
and 'cast'. Your data is all ready "molten", i.e. it is in the long
format (in the terminology of the base reshape function) with
identifier values in each row and a single column of values.
> library(reshape)
> cast(dataframe,A~B)
Using C as value column. Use the value argument to cast to override
this choice
A control sample
1 d0 1e+05 1e+05
2 d1 2e+02 3e+02
3 d2 4e+02 5e+02
Basically the cast formula keeps the LHS variables in the rows and hte
RHD variables get arranges in columns. (For reasons that are unclear
to me the dataframe argument was placed first when using positional
argument passing, unlike most other formula methods in R.)
--
David Winsemius, MD
West Hartford, CT
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