Tidyverse gather with rowdata from other data frame

Question

I have been searching for quite some time to an elegant solution to this problem, to no avail. So I decided to give it a go here.

I am using tidyverse, and

Answer 1

The *_join functions from dplyr (loaded with tidyverse) are great for solving lots of problems involving more than one dataframe.

> df %>%
      gather(sample, value, -annot) %>%
      left_join(sample_info, by = 'sample')

  annot  sample value  condition
1     A sample1     1   infected
2     B sample1     1   infected
3     C sample1     4   infected
4     D sample1     2   infected
5     A sample2     3 uninfected
6     B sample2     5 uninfected
7     C sample2     4 uninfected
8     D sample2     5 uninfected