R studio: How to transform columns to multiple rows as factos

Question

I'm currently working with RStudio and I'm having some problems. I've researched some functions (reshape,merge, combine, etc.) but couldn't get my problem solved.

I have this kind of data in excel:

    ID_No Measurament_1 Measurament_2 Measurament_3 Measurament_4
1 a                1            2            3            4
2 b                5            6            7            8
3 c                10           20           30           40
4 d                60           70           80           90 

and I want to transform it in this way:

ID_No        Measurament
 1 a              1
 2 a              2
 3 a              3
 4 a              4
 5 b              5
 6 b              6
 7 b              7
 8 b              8
 9 c              10
10 c              20
11 c              30
12 c              40
13 d              60
14 d              70
15 d              80
16 d              90

Can you guys help me out? There should be an easy command for this task but I don't get it.

Answer 1

You can try with df your dataframe:

library(reshape2)
df2 <- melt(df,idvar='ID_No')

Answer 2

There's also the Tidyverse way of doing it, which gives you a lot of control over what columns you want to make long instead of wide:

library(dplyr)
library(tidyr)
measurements <- data.frame(ID_No=c("a", "b", "c", "d"), 
                           m_1=c(1,5,10,60),
                           m_2=c(2, 6, 20, 70),
                           m_3=c(3, 7, 30, 80),
                           m_4=c(4, 8, 40, 90),
                           stringsAsFactors = FALSE
)
measurements %>% pivot_longer(cols = starts_with("m_"),
                              values_to = "Measurement")

This additionally gives you the original field names (m_1, m_2, etc.) as another column, if you want to track that as well. If not, you can can just drop that column.