how to transform rows to columns in R

Question

I would like to know how to transform rows to columns for the following dataset.

School class Avg  Subavg  Sub
ABC     2    25.3  17.2   Geo
ABC     2    25.3  18.2   Mat
ABC     2    25.3  20.2   Fre
ABC     3    21.2  17.2   Geo
ABC     3    21.2  18.2   Mat
ABC     3    21.2  20.2   Ger
ABC     4    16.8  17.2   Ger
ABC     4    16.8  18.2   Mat
ABC     5    20.2  20.2   Fre

Expected output would be

School Std stdavg  Geo   mat    Ger     Fer
ABC    2    25.3   17.2  18.2   NA      20.2
ABC    3    21.2   17.2  18.2   20.2    NA
ABC    4    25.3   NA    18.2   17.2    NA
ABC    5    25.3   NA    NA     NA      20.2

I used split function, But in vain.

Thanks in advance

Answer 1

We can use dcast

library(data.table)
dcast(setDT(df1), School+class+Avg~Sub, value.var="Subavg")
#    School class  Avg  Fre  Geo  Ger  Mat
#1:    ABC     2 25.3 20.2 17.2   NA 18.2
#2:    ABC     3 21.2   NA 17.2 20.2 18.2
#3:    ABC     4 24.8   NA   NA 17.2 18.2
#4:    ABC     5 24.8 20.2   NA   NA   NA

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Or use spread from tidyr

library(tidyr)
spread(df1, Sub, Subavg)