Reshape data frames - tidyr

Install required packages

dplyr, tidyr

wants <- c("dplyr", "tidyr")
has   <- wants %in% rownames(installed.packages())
if(any(!has)) install.packages(wants[!has])

Simulate data

Nj    <- 2
P     <- 2
Q     <- 3
id    <- 1:(P*Nj)
DV_t1 <- round(rnorm(P*Nj, -1, 1), 2)
DV_t2 <- round(rnorm(P*Nj,  0, 1), 2)
DV_t3 <- round(rnorm(P*Nj,  1, 1), 2)
IVbtw <- factor(rep(c("A", "B"), Nj))
(datW <- data.frame(id, IVbtw, DV_t1, DV_t2, DV_t3))

  id IVbtw DV_t1 DV_t2 DV_t3
1  1     A -1.07 -0.47  2.38
2  2     B  0.85  1.39  0.45
3  3     A  0.14  1.85  2.53
4  4     B -1.79 -0.20  1.00

Wide format -> long format

library(dplyr)
library(tidyr)

datL <- datW %>%
    pivot_longer(cols=starts_with("DV_"),
                 names_to="time", values_to="DV",
                 names_prefix="DV_")

datL

# A tibble: 12 x 4
      id IVbtw time     DV
   <int> <fct> <chr> <dbl>
 1     1 A     t1    -1.07
 2     1 A     t2    -0.47
 3     1 A     t3     2.38
 4     2 B     t1     0.85
 5     2 B     t2     1.39
 6     2 B     t3     0.45
 7     3 A     t1     0.14
 8     3 A     t2     1.85
 9     3 A     t3     2.53
10     4 B     t1    -1.79
11     4 B     t2    -0.2 
12     4 B     t3     1   

Long format -> wide format

One variable

datL %>%
    pivot_wider(id_cols=c(id, IVbtw),
                names_from=time, values_from=DV,
                names_prefix="DV_")

# A tibble: 4 x 5
     id IVbtw DV_t1 DV_t2 DV_t3
  <int> <fct> <dbl> <dbl> <dbl>
1     1 A     -1.07 -0.47  2.38
2     2 B      0.85  1.39  0.45
3     3 A      0.14  1.85  2.53
4     4 B     -1.79 -0.2   1   

Two variables

datL %>%
    mutate(DVsq=DV^2) %>%
    pivot_wider(id_cols=c(id, IVbtw),
                names_from=time, values_from=c(DV, DVsq))

# A tibble: 4 x 8
     id IVbtw DV_t1 DV_t2 DV_t3 DVsq_t1 DVsq_t2 DVsq_t3
  <int> <fct> <dbl> <dbl> <dbl>   <dbl>   <dbl>   <dbl>
1     1 A     -1.07 -0.47  2.38  1.14     0.221   5.66 
2     2 B      0.85  1.39  0.45  0.722    1.93    0.202
3     3 A      0.14  1.85  2.53  0.0196   3.42    6.40 
4     4 B     -1.79 -0.2   1     3.20     0.04    1    

Detach (automatically) loaded packages (if possible)

try(detach(package:dplyr))
try(detach(package:tidyr))

Get the article source from GitHub

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