用日期从长到宽重塑 - R

Question

Can someone tell me why I'm having trouble reshaping with dates. I'd like to go from here:

#Data frame
date = c("01/03/15", "03/04/12", "07/21/16","09/08/16") 
id = c(1,1,2,2) 
df = data.frame(id,date)

#Convert to date
df$date <- as.Date(df$date, "%m/%d/%y")

#Reshape
library(reshape)
a <- reshape(df, idvar = "id", timevar = "date", direction = "wide")

to here:

#Final date frame
date.2 = c("03/04/12", "09/08/16") 
date.1 = c("01/03/15", "07/21/16") 
id = c(1,2) 
df = data.frame(id,date.1,date.2)

Thanks for your help.

Answer 1

We can use dcast

library(data.table)
dcast(setDT(df), id~paste0("date.", rowid(id)), value.var = "date")
#   id     date.1     date.2
#1:  1 2015-01-03 2012-03-04
#2:  2 2016-07-21 2016-09-08

---

Or using tidyverse

library(dplyr)
library(tidyr)
df %>%
  group_by(id) %>% 
  mutate(i1 = paste0("date.", row_number())) %>%
  spread(i1, date)