I have a df including a set of data frames, df1, df2, and df3 where each data frame follow this structure:
df1 <- data.frame(year = c("2013", "2013", "2013", "2013", "2013","2013"),
site = c("a", "a", "a", "a", "a", "a"),
trt = c("x", "y", "x", "y", "x", "y"),
cover = c(2, 5, 1,20,50,12))
df2 <- data.frame(year = c("2014", "2014", "2014", "2014", "2014","2014"),
site = c("a", "a", "a", "a", "a", "a"),
trt = c("x", "y", "x", "y", "x", "y"),
cover = c(1, 3, 1,24,32,12))
df3 <- data.frame(year = c("2015", "2015", "2015", "2015", "2015","2015"),
site = c("a", "a", "a", "a", "a", "a"),
trt = c("x", "y", "z", "z", "x", "y"),
cover = c(2, 5, 1,2,11,32))
df <- rbind(df1, df2, df3)
df
year site trt cover
1 2013 a x 2
2 2013 a y 5
3 2013 a x 1
4 2013 a y 20
5 2013 a x 50
6 2013 a y 12
7 2014 a x 1
8 2014 a y 3
9 2014 a x 1
10 2014 a y 24
11 2014 a x 32
12 2014 a y 12
13 2015 a x 2
14 2015 a y 5
15 2015 a z 1
16 2015 a z 2
17 2015 a x 11
18 2015 a y 32
I used to rank the values in the cover column for each year, using a for loop.
v1 <- unique(df$year)
lst <- list()
for (i in seq_along(v1)) {
lst[[i]] <- df |>
filter(year == v1[i]) |>
mutate(rank = dense_rank(desc(cover)))
}
Now, I am trying to rank the values of each group (as defined in the trt column) for each year, but I am having trouble figuring out how to do so. How can I do this with for loop. I am open to get an answer with lapply function as I would like to learn about it.
Using dplyr, we can avoid the loop and the filtering by using group before mutate, and then construct the list using group_split.
library(dplyr)
df |>
group_by(year) |>
mutate(rank = dense_rank(desc(cover))) |>
group_split()
Output:
[[1]]
# A tibble: 6 × 5
year site trt cover rank
<chr> <chr> <chr> <dbl> <int>
1 2013 a x 2 5
2 2013 a y 5 4
3 2013 a x 1 6
4 2013 a y 20 2
5 2013 a x 50 1
6 2013 a y 12 3
[[2]]
# A tibble: 6 × 5
year site trt cover rank
<chr> <chr> <chr> <dbl> <int>
1 2014 a x 1 5
2 2014 a y 3 4
3 2014 a x 1 5
4 2014 a y 24 2
5 2014 a x 32 1
6 2014 a y 12 3
[[3]]
# A tibble: 6 × 5
year site trt cover rank
<chr> <chr> <chr> <dbl> <int>
1 2015 a x 2 4
2 2015 a y 5 3
3 2015 a z 1 5
4 2015 a z 2 4
5 2015 a x 11 2
6 2015 a y 32 1