Help with gather()

tidyverse
1

Hi,

I am new to R. I'd like to gather the iris data set into a table that looks like this:

Species Component Quantity Value
setosa Sepal Length 5.1
setosa Sepal Length 4.9
...

How should I use gather()? Thanks in advance for any help.

2 
library(tidyverse)

iris %>% 
  gather("Component", "Value", -Species)

See documentation here:

3

pivot_longer() is the new gather() and more intuitive. https://tidyr.tidyverse.org/reference/pivot_longer.html

2 Likes
4

Martin, thank you for this.

After gather(), I want to pipe into a separate() function, since I need to split the column containing "Sepal.Length" into 2 columns, using the fullstop as the separator. This is what I did:

tidy = iris %>%
  gather("Component", "Value", -Species) %>% 
  separate(Component, c("Component", "Quantity"), sep = ".")

This gives me this error:

Expected 2 pieces. Additional pieces discarded in 600 rows [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, ...].

If remove the argument sep = "." from separate, the code runs fine.

Any idea what the issue may be?

6

Hi, thank you for the recommendation. I have to stick to gather() for now though.

7 
library(tidyverse)

iris %>% 
  as_tibble() %>% # not required
  gather("Component", "Value", -Species) %>% 
  separate(Component, c("Component", "Quantity"), sep = "\\.")

You've stumbled on an issue introduced by regex. A single "." means any single character. The two "\" backslashes "escape" the expression meaning that the literal "." becomes the separator.

8

That works perfectly now, thanks!

9

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