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I've got a data set that I want to group the data by 'Location' and by 'Site; and then subtract first 'value' of each 'Plate' from rest of the values ? Output should looks like this;

Location Site Plate value diff
NR Site B  Plate 1 220 0
NR Site B  Plate 1 207 -13
NR Site B  Plate 1 203 -17
NR Site B  Plate 2 183 0
NR Site B  Plate 2 173 -10
NR Site B  Plate 2 180 -3
NR Site B  Plate 3 191 0
NR Site B  Plate 3 190 -1
NR Site B  Plate 3 190 -1
FB Site A  Plate 1 235 0
FB Site A  Plate 1 240 5
FB Site A  Plate 1 236 1
FB Site A  Plate 2 250 0
FB Site A  Plate 2 244 -6
FB Site A  Plate 2 250 0
FB Site B  Plate 7 144 0
FB Site B  Plate 7 116 -28
FB Site B  Plate 7 110 -34
nuwanma
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1 Answers1

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library(tidyverse)
df1 %>% 
  group_by(Location, Site) %>% 
  mutate(
    diff = platvalue - platvalue[1]
  )
Zhiqiang Wang
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