CODEWITHSUNDEEP
rdplyr
JFD
JFD

Reputation: 339

Subtract a value from one variable by second variable using dplyr

I have time dependent data that includes "year" as a column and is the year of the data. I have a second variable, with one value per year, that I'd like to substract from the first variable when the years are identical. 

library(dplyr)

a1 = data.frame(year = 2000:2005, y=0:5)
b1 = data.frame(year = 2000:2005, y=0:5)
ab = rbind(a1,b1)

c1 = data.frame(year = 2000:2005, x = 10:15)

# my best attempt - does not work
result <- ab %>% group_by(year) %>% mutate(diff = year - c1[year])

what I expect is that result has an entry with year = 2000, y = 0, and a new column diff = -10.

But, can't seem to make that work using dplyr.

How can this be accomplished using dplyr?

Upvotes: 0

Views: 226

Answers (1)

william3031
william3031

Reputation: 1708

Is there a difference between a1 and b1? They look the same.

How about this?

d <- left_join(ab, c1, by = "year") %>% 
  mutate(diff = y-x)

Gives me this, which seems to solve your problem.

   year y  x diff
1  2000 0 10  -10
2  2001 1 11  -10
3  2002 2 12  -10
4  2003 3 13  -10
5  2004 4 14  -10
6  2005 5 15  -10
7  2000 0 10  -10
8  2001 1 11  -10
9  2002 2 12  -10
10 2003 3 13  -10
11 2004 4 14  -10
12 2005 5 15  -10

Upvotes: 1

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