Re-organizing a dataframe

Question

I am trying to re-organize my data frame using reshape2 library. Even though convincing, I am not able to get the expected result.

Here is my data.frame on hand.

   > mydata                
       Destination S1 S2 S3 S4
    1           D1 94 87 84 75
    2           D2 94 87 84 75
    3           D3 94 87 84 75
    4           D4 10 95 92 83

Here is what I am expecting.

Source  Destination Value
    S1      D1      94
    S2      D1      87
    S3      D1      84
    S4      D1      75
    S1      D2      94
    S2      D2      87
    S3      D2      84
    S4      D2      75
    S1      D3      94
    S2      D3      87
    S3      D3      84
    S4      D3      75
    S1      D4      10
    S2      D4      95
    S3      D4      92
    S4      D4      83

I tried to transpose the data.frame, using the below:

> mydata.T <- t(mydata[,2:ncol(mydata)])
> 
> mydata.T
S1   94   94   94   10
S2   87   87   87   95
S3   84   84   84   92
S4   75   75   75   83

I tried with melt, but I am not able to get the exact result.

Can someone please help me here?

Answer 1

What's wrong with using transpose on your data.frame?

If you want to use "reshape2", you can try the following:

mydataLong <- melt(mydata, id.vars="Destination")
mydataLong
#    Destination variable value
# 1           D1       S1    94
# 2           D2       S1    94
# 3           D3       S1    94
# 4           D4       S1    10
# 5           D1       S2    87
# 6           D2       S2    87
# 7           D3       S2    87
# 8           D4       S2    95
# 9           D1       S3    84
# 10          D2       S3    84
# 11          D3       S3    84
# 12          D4       S3    92
# 13          D1       S4    75
# 14          D2       S4    75
# 15          D3       S4    75
# 16          D4       S4    83

In base R, you can try the following for the long output:

cbind(mydata[1], stack(mydata[-1]), row.names = NULL)

If you wanted that compact transposed output, you would do this:

dcast(mydataLong, variable ~ Destination)
#   variable D1 D2 D3 D4
# 1       S1 94 94 94 10
# 2       S2 87 87 87 95
# 3       S3 84 84 84 92
# 4       S4 75 75 75 83

Answer 2

data.frame(Destination=mydata$Destination, Value=as.vector(data.matrix(mydata[-1]) ))

My gues is that this came from a table operation ans should have been:

 as.data.frame(table( something ) )