merge list elements which are different dimensions r [duplicate]

Answer 1

We can gather data to long form excluding year and Area column, unite the year and then spread it to wide format.

library(dplyr)
library(tidyr)

df %>%
  gather(key, value, -year, -Area) %>%
  unite(key, key, year, sep = "") %>%
  spread(key, value)

#  Area N2017 N2018 P2017 P2018
#1    1     5     1     5     1
#2    2     6     2     6     2
#3    3     7     3     7     3
#4    4    NA     4    NA     4

Answer 2

We can do this with dcast from data.table which can take multiple value.var columns

library(data.table)
dcast(setDT(df), Area ~ year, value.var = c("P", "N"))
#  Area P_2017 P_2018 N_2017 N_2018
#1:    1      5      1      5      1
#2:    2      6      2      6      2
#3:    3      7      3      7      3
#4:    4     NA      4     NA      4