将 dataframe 中的 R 中的列压缩为 2 列（索引和值）

Question

The initial dataframe is something like

ProductID  Month_1   Month_2    Month_3
1           50       50         0
2           0        400        0    
3           0        0          20  

values for each month are listed in a separate column for each product. I'm trying to condense these columns into a generic identifier & value column and am running into trouble.

The ideal output looks something like this

ProductID  Month   Value 
1           1       50
1           2       30
2           2       400  
3           3       20   

Answer 1

We can use pivot_longer and filter the elements not equal to 0

library(dplyr)
library(tidyr)
pivot_longer(df1, cols = -ProductID, names_to = c(".value", "month"), 
        names_sep = "_") %>% 
  filter(Month != 0)