Reshape horizontal to to long format using pivot_longer - r

Question

I am trying to reshape my data to long instead of wide format using the same code provided earlier link , however it doesn't work even after several trials to modify names_pattern = "(.*)_(pre|post.*)",
My data sample is
data1<-read.table(text="
Serial_ID pre_EDV pre_ESV pre_LVEF post_EDV post_ESV post_LVEF
1 76.2 32.9 56.8 86.3 36.6 57.6
2 65.4 35.9 45.1 60.1 26.1 56.7
3 64.4 35.1 45.5 72.5 41.1 43.3
4 50 13.9 72.1 46.4 18.4 60.4
5 89.6 32 64.3 70.9 19.3 72.8
6 62 20.6 66.7 55.9 17.8 68.2
7 91.2 37.7 58.6 61.9 23.8 61.6
8 62 24 61.3 69.3 34.9 49.6
9 104.1 22.7 78.8 38.6 11.5 70.1
10 90.6 31.2 65.6 48 16.1 66.4", sep="", header=T)
I want to reshape my data to
put identical column headings below each other eg post_EDV below
pre_EDV
Create new column Pre vs. post
Fix column heading (remove "pre_" and "post_" to be "EDV" only (as shown in the screenshot below)).
This is the used code:
library(dplyr);library(tidyr);library(stringr)
out <- data %>% pivot_longer(cols = -Serial_ID,
names_to = c(".value", "prevspost"),
names_pattern = "(.*)_(pre|post.*)",
names_sep="_") #%>% as.data.frame
Also I tried names_prefix = c("pre_","post_") instead of names_pattern = "(.*)_(pre|post.*)", but it doesn't work.
Any advice will be greatly appreciated.

Answer 1

Edit I recommend using #Dave2e's superior approach.
The reason your attempt didn't work is because the pattern has to match in order. You could try this:
library(tidyr)
library(dplyr)
data1 %>% pivot_longer(cols = -Serial_ID,
names_to = c("prevspost",".value"),
names_pattern = "(pre|post)_(\\w+)") %>%
dplyr::arrange(desc(prevspost),Serial_ID)
# A tibble: 20 x 5
Serial_ID prevspost EDV ESV LVEF
<int> <chr> <dbl> <dbl> <dbl>
1 1 pre 76.2 32.9 56.8
2 2 pre 65.4 35.9 45.1
3 3 pre 64.4 35.1 45.5
4 4 pre 50 13.9 72.1
5 5 pre 89.6 32 64.3
6 6 pre 62 20.6 66.7
7 7 pre 91.2 37.7 58.6
8 8 pre 62 24 61.3
9 9 pre 104. 22.7 78.8
10 10 pre 90.6 31.2 65.6
11 1 post 86.3 36.6 57.6
12 2 post 60.1 26.1 56.7
13 3 post 72.5 41.1 43.3
14 4 post 46.4 18.4 60.4
15 5 post 70.9 19.3 72.8
16 6 post 55.9 17.8 68.2
17 7 post 61.9 23.8 61.6
18 8 post 69.3 34.9 49.6
19 9 post 38.6 11.5 70.1
20 10 post 48 16.1 66.4

Answer 2

Your initial approach very close, it needed some simplification. Use only "names_sep" or "names_pattern"
library(tidyr)
library(dplyr)
data1 %>% pivot_longer(cols = -Serial_ID,
names_to = c("Pre vs. post", '.value'),
names_sep="_")
# A tibble: 20 x 5
Serial_ID `Pre vs. post` EDV ESV LVEF
<int> <chr> <dbl> <dbl> <dbl>
1 1 pre 76.2 32.9 56.8
2 1 post 86.3 36.6 57.6
3 2 pre 65.4 35.9 45.1
4 2 post 60.1 26.1 56.7
5 3 pre 64.4 35.1 45.5
6 3 post 72.5 41.1 43.3
7 4 pre 50 13.9 72.1
8 4 post 46.4 18.4 60.4
9 5 pre 89.6 32 64.3
10 5 post 70.9 19.3 72.8
11 6 pre 62 20.6 66.7
12 6 post 55.9 17.8 68.2
13 7 pre 91.2 37.7 58.6
14 7 post 61.9 23.8 61.6
15 8 pre 62 24 61.3
16 8 post 69.3 34.9 49.6
17 9 pre 104. 22.7 78.8
18 9 post 38.6 11.5 70.1
19 10 pre 90.6 31.2 65.6
20 10 post 48 16.1 66.4

Answer 3

try this:
library(dplyr);library(tidyr);library(stringr)
out <- data1 %>% pivot_longer(-Serial_ID,
names_to = c("measurement", "names"),
values_to = "values",
names_sep = "_")
out
# # A tibble: 60 x 4
# Serial_ID measurement names values
# <int> <chr> <chr> <dbl>
# 1 1 pre EDV 76.2
# 2 1 pre ESV 32.9
# 3 1 pre LVEF 56.8
# 4 1 post EDV 86.3
# 5 1 post ESV 36.6
# 6 1 post LVEF 57.6
# 7 2 pre EDV 65.4
# 8 2 pre ESV 35.9
# 9 2 pre LVEF 45.1
# 10 2 post EDV 60.1
# # ... with 50 more rows
Your code snipped passed the object "data" instead of "data1" into the pipe which produced an error:
"Error: No tidyselect variables were registered".