On Aug 20, 2011, at 1:21 PM, Uwe Ligges wrote:
On 20.08.2011 19:04, David Winsemius wrote:
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.
David,
I think there are some good examples on the help page. What is
missing? What is not clearly explained?
The stumbling blocks I have encountered are in trying to figure out
which of the multiple arguments are needed a) in going from wide to
long and b) in going from long to wide, c) and what are the reasons
for the various error messages I provoke . I am almost never able to
do it correctly on the first try and rarely able to do it even on the
fourth try. I bought Spector's book in hopes of understanding it
better, but his efforts did not take root in my brain.
In the instance above, how would I have know how to apply the help
page description of timevar (below) to this problem?
timevar
the variable in long format that differentiates multiple records from
the same group or individual.
To my reading that does not distinguish the purpose of 'timevar' from
the purpose of 'idvar' and then reading the 'idvar' definition just
below it does not help at all.
--
David.
If a longer tutorial is needed, that may be an article for the R
Help Desk in The R Journal. Anybody volunteering?
Best,
Uwe
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
______________________________________________
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
and provide commented, minimal, self-contained, reproducible code.
