R: Adding NAs into Data Frame

Question

I have a data frame like so:

Name   Position   Value
a         1        0.2
a         3        0.4
a         4        0.3
b         1        0.5
b         2          


        

Answer 1

You could use data.table

 library(data.table)
 DT <- data.table(df)
 setkey(DT, Position)
 DT[, .SD[J(1:5), roll=FALSE], by=Name][order(Name, Position),]
 #   Name Position Value
 #1:    a        1   0.2
 #2:    a        2    NA
 #3:    a        3   0.4
 #4:    a        4   0.3
 #5:    a        5    NA
 #6:    b        1   0.5
 #7:    b        2   0.4
 #8:    b        3    NA
 #9:    b        4    NA
#10:    b        5   0.3
#11:    c        1    NA
#12:    c        2   0.3
#13:    c        3   0.4
#14:    c        4    NA
#15:    c        5   0.1
#16:    d        1   0.2
#17:    d        2   0.4
#18:    d        3   0.5
#19:    d        4    NA
#20:    d        5    NA

Or you can use tidyr/dplyr

 library(dplyr)
 library(tidyr)

  df %>% 
      spread(Position, Value) %>%
      gather(Position, Value, `1`:`5`) %>%
      arrange(Name, Position)    

data

 df <- structure(list(Name = c("a", "a", "a", "b", "b", "b", "c", "c", 
 "c", "d", "d", "d"), Position = c(1L, 3L, 4L, 1L, 2L, 5L, 2L, 
 3L, 5L, 1L, 2L, 3L), Value = c(0.2, 0.4, 0.3, 0.5, 0.4, 0.3, 
 0.3, 0.4, 0.1, 0.2, 0.4, 0.5)), .Names = c("Name", "Position", 
 "Value"), class = "data.frame", row.names = c(NA, -12L))