How to split a column in R? [duplicate]

Answer 1

library(reshape2)

dcast(df, class ~ grade, value.var = "score")
  class  a  b
1     1 12 45
2     2 45 92
3     3 75 78
4     4 18 36
5     5  6 39

df <- structure(list(class = c(1L, 2L, 3L, 4L, 5L, 1L, 2L, 3L, 4L, 
5L), grade = structure(c(1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 
2L), .Label = c("a", "b"), class = "factor"), score = c(12L, 
45L, 75L, 18L, 6L, 45L, 92L, 78L, 36L, 39L)), .Names = c("class", 
"grade", "score"), class = "data.frame", row.names = c(NA, -10L
))

Answer 2

Another option is spread from library(tidyr)

library(tidyr)
spread(df1, grade, score)

Answer 3

Base R's unstack does this out of the box:

unstack(df, score ~ grade)
#   a  b
#1 12 45
#2 45 92
#3 75 78
#4 18 36
#5  6 39

As does xtabs:

as.data.frame.matrix(xtabs(score ~ class + grade, data=df))

#   a  b
#A 12 45
#B 45 92
#C 75 78
#D 18 36
#E  6 39