how to change my dataframe based on value of a column

Question

there is a dataframe with two column as below,and i want to change it into a dataframe with 3 column

df <- data.frame(key=c('a','a','a','b','b'),value=c(1,2,2,1,3))

I have tried it in python,that's ok,but in r i have no idea

the expect output should be like

  1 2 3
a 1 2 0
b 1 0 1

`table` should help `table(df)` – Ronak Shah Jul 17 '19 at 01:07 — Ronak Shah, Jul 17 '19 at 01:07

score 0 · Answer 1 · answered Jul 17 '19 at 01:04

0

library(data.table)
dcast(key~value, data=df, fun.aggregate=length)
#   key 1 2 3
# 1   a 1 2 0
# 2   b 1 0 1

answered Jul 17 '19 at 01:04

r2evans

1 Answers1