reshape data by ID and add all values belong to one person in one row in R

Question

I have a data frame looks like this:

ID  V1 V2  V3
1   1  2   3
1   2  3   4
1   3  4   5
2   3  4   5
3   4  5   6
3   2  3   4

I need to reshape the data frame so that all the records belong to one person present in the same row like this:

ID V1 V2 V3 V1_2 V2_2 V3_2 V1_3 V2_3 V3_3
1  1  2  3  2     3    4    3    4    5
2  3  4  5
3  4  5  6  2     3    4  

Because each person has different number of records, the new data frame will have different length in each row. How can I achieve this?

Answer 1

One straightforward way is with the reshape2 package, but you must add a secondary ID.

### The next line creates a secondary ID variable
mydf$ID2 <- ave(mydf$ID, mydf$ID, FUN = seq_along)

library(reshape2)
dfL <- melt(mydf, id.vars=c("ID", "ID2"))
dcast(dfL, ID ~ variable + ID2)
#   ID V1_1 V1_2 V1_3 V2_1 V2_2 V2_3 V3_1 V3_2 V3_3
# 1  1    1    2    3    2    3    4    3    4    5
# 2  2    3   NA   NA    4   NA   NA    5   NA   NA
# 3  3    4    2   NA    5    3   NA    6    4   NA

Alternatively, after having added "ID2" as indicated above, you can also do the reshaping directly with base R's reshape. The column orders are different, but the data is the same.

reshape(mydf, direction = "wide", idvar="ID", timevar="ID2")
#   ID V1.1 V2.1 V3.1 V1.2 V2.2 V3.2 V1.3 V2.3 V3.3
# 1  1    1    2    3    2    3    4    3    4    5
# 4  2    3    4    5   NA   NA   NA   NA   NA   NA
# 5  3    4    5    6    2    3    4   NA   NA   NA