Reordering dcast data frame

Question

Is it possible to reorder the columns of data frame which is a result of dcast() call E.x.

Given the data:

> dput(copyOfRes)
structure(list(docName = c("doc2", "doc1", "doc1", "doc1", "doc1", 
"doc1", "doc1", "doc1", "doc1", "doc1", "doc1", "doc2"), day_of_week = c(11, 
11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 2)), .Names = c("docName", 
"week_number"), row.names = c(NA, -12L), class = "data.frame")

So, when I use dcast() as follows:

library(reshape2)
dcast(copyOfRes, docName ~ week_number, length)

the result is:

  docName 2 11
1    doc1 0 10
2    doc2 1  1

I would like to have the data frame with decreasing value of week_number as follows:

  docName 11  2
1    doc1 10 0
2    doc2 1  1

I tried doing dcast(copyOfRes, docName ~ sort(week_number, decreasing= TRUE), length), but it still does not work. Any suggestions?

Answer 1

You can use factor() inside dcast() set appropriate order of levels.

 dcast(copyOfRes, 
   docName ~ factor(week_number,levels=unique(week_number)), length)
      docName 11 2
    1    doc1 10 0
    2    doc2  1 1

Answer 2

You can use reorder here with rev

dcast(copyOfRes, docName ~ reorder(week_number,rev(week_number)), length)
Using week_number as value column: use value.var to override.
  docName 11 2
1    doc1 10 0
2    doc2  1 1