[R] how to "singlify" entries

[Gabor Grothendieck]

On 5/30/05, Charles Plessy <charles-r-nospam at plessy.org> wrote:
> On Mon, May 30, 2005 at 09:15:32AM +0000, zhihua li wrote :
> > hi netters
> >
> > I have a rather simple question.  I have a data frame with two variables X
> > and Y, both of which are factors. X has 100 levels while Y has 10 levels
> > only. The data frame has 100 rows in all, so for X the values are unique,
> > and Y has many replicate values.  Now I wanna reduce the data frame into 10
> > rows only, according to the 10 levels of Y.  I don't care which value of X
> > is in the same row with Y in the final data frame, as long as it is in
> > agreement with the original data frame.
> 
> Dear list,
> 
> I am a new subscriber, using R to analyse genomics data. I have a
> similar question, maybe even identical, but I am not sure...
> 
> >From a data frame with two factors and one value, I would like to obtain a data
> frame with one factor and one value per level in the removed factor.
> 
> For instance:
> 
> F1      F2      V
> -----------------
> A       X       3
> A       Y       6
> B       X       5
> C       X       9
> C       Y       3
> 
> Would become:
> 
> F1      VX      VY
> ------------------
> A       3       6
> B       5       0
> C       9       3
> 
> I am sure I have seen a tool to do this some time ago, but I do not remember
> its name.
> 
Try using reshape, e.g. if dd is your data frame:

reshape(dd, dir = "wide", idvar = "F1", timevar = "F2", 
    varying = list(c("VX","VY")))