If two values in the same column match, return value from the same row from another column-CodePudding

I've a dataframe like that

Polygon_No     shp Sp.       area 
    2           4 T.a.       31429.
    2           4 T.n.       0 
    2           6 B.a.       0  
    2           6 T.a.       15714.

I want to replace the 0 in area column with value in the same column

I mean if area == 0 & shp cell values matches (6&6) & Polygon_No (2&2) replace 0 with 15714.

CodePudding user response：

I'd prefer max and dplyr::group_by with dplyr::mutate:

df %>% group_by(Polygon_No, shp) %>%
   mutate(area=max(area))

Output:

  Polygon_No   shp Sp.    area
       <int> <int> <chr> <dbl>
1          2     4 T.a.  31429
2          2     4 T.n.  31429
3          2     6 B.a.  15714
4          2     6 T.a.  15714

CodePudding user response：

You may try

library(dplyr)
df %>%
  group_by(Polygon_No, shp) %>%
  mutate(area = ifelse(area>0, area, NA)) %>%
  mutate(area = unique(area[!is.na(area)]))

  Polygon_No   shp Sp.    area
       <int> <int> <chr> <dbl>
1          2     4 T.a.  31429
2          2     4 T.n.  31429
3          2     6 B.a.  15714
4          2     6 T.a.  15714