按R中的组转置数据

Question

I have data in the following structure:

x <- read.table(header=T, text="
X Y D S
a e 1 10
a e 2 20
a f 1 50
b c 1 40
b c 2 30
b c 3 60
b d 1 10 
b d 2 20")

And I want to get the following result:

X Y   1   2   3
a e  10  20
a f  50
b c  40  30  60
b d  10  20

For every combination of columns X and Y I would like to transpose data in column S by order in column D .

I thought xtabs() will work, but I don't think so, my best version is:

xtabs(formula=S~Y+D,data=x)

With result:

   D
Y    1  2  3
  c 40 30 60
  d 10 20  0
  e 10 20  0
  f 50  0  0

Answer 1

require(reshape2)
dcast(x, X + Y ~ D, value.var="S")

If you want to fill empty entries with 0 instead of NA (which is the default), then,

dcast(x, X + Y ~ D, value.var="S", fill=0)

Answer 2

A solution in base R:

> reshape(x, timevar="D", idvar=c("X","Y"), direction="wide")
  X Y S.1 S.2 S.3
1 a e  10  20  NA
3 a f  50  NA  NA
4 b c  40  30  60
7 b d  10  20  NA

Answer 3

The other two answers are very good, but for what it's worth, since you mentioned you started your attempts with xtabs , you can get close to what you were looking for with a combination of xtabs and ftable . However, the result will include all factor levels

ftable(xtabs(S ~ ., x))
#     D  1  2  3
# X Y           
# a c    0  0  0
#   d    0  0  0
#   e   10 20  0
#   f   50  0  0
# b c   40 30 60
#   d   10 20  0
#   e    0  0  0
#   f    0  0  0

Alternatively, you can do something like this:

data.frame(unique(x[1:2]), 
           as.data.frame.matrix(xtabs(S ~ do.call(paste, x[1:2]) + D, x)))
#   X Y X1 X2 X3
# 1 a e 10 20  0
# 3 a f 50  0  0
# 4 b c 40 30 60
# 7 b d 10 20  0