Hi,
I have an easy question. I have dataframe:
df <- data.frame(
stringsAsFactors = FALSE,
a= c(1,1,1,1,1,2,2,2,2,3,3),
b = c("a","a","b","b","c","a","a","a","b","a","a"),
c= c(11,22,33,44,55,66,77,88,99,12,14)
)
and I would like to sum values in 'c' for groups of rows with the same values in 'a' and 'b' and add these sums as a new column 'd' to this dafaframe for each group of rows (sharing the same values in 'a' and 'b').
Many thanks
This is a job for group_by() and summarise().
library(dplyr, warn.conflicts = FALSE)
df <- data.frame(
stringsAsFactors = FALSE,
a = c(1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3),
b = c("a", "a", "b", "b", "c", "a", "a", "a", "b", "a", "a"),
c = c(11, 22, 33, 44, 55, 66, 77, 88, 99, 12, 14)
)
df %>%
group_by(a, b) %>%
summarise(d = sum(c), .groups = "drop")
#> # A tibble: 6 x 3
#> a b d
#> <dbl> <chr> <dbl>
#> 1 1 a 33
#> 2 1 b 77
#> 3 1 c 55
#> 4 2 a 231
#> 5 2 b 99
#> 6 3 a 26
Created on 2020-06-10 by the reprex package (v0.3.0)
Actually, I wanted to keep all the rows and just add a new column. Could you help me with that?
i.e.
a b c d
1 a 11 33
1 a 22 33
1 b 33 77
1 b 44 77
....
Many thanks
....
Use mutate() instead.
library(dplyr, warn.conflicts = FALSE)
df <- data.frame(
stringsAsFactors = FALSE,
a = c(1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3),
b = c("a", "a", "b", "b", "c", "a", "a", "a", "b", "a", "a"),
c = c(11, 22, 33, 44, 55, 66, 77, 88, 99, 12, 14)
)
df %>%
group_by(a, b) %>%
mutate(d = sum(c))
#> # A tibble: 11 x 4
#> # Groups: a, b [6]
#> a b c d
#> <dbl> <chr> <dbl> <dbl>
#> 1 1 a 11 33
#> 2 1 a 22 33
#> 3 1 b 33 77
#> 4 1 b 44 77
#> 5 1 c 55 55
#> 6 2 a 66 231
#> 7 2 a 77 231
#> 8 2 a 88 231
#> 9 2 b 99 99
#> 10 3 a 12 26
#> 11 3 a 14 26
Created on 2020-06-11 by the reprex package (v0.3.0)
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