Using piping in R (with %>%
), how can one pass specific vector elements from a function's output to feed the next function's arguments?
I've tried using the dot operator with position in braces (i.e., .[1], .[2]
) to no avail.
The only way that was working for me was with sapply()
, but I'm wondering whether there's a simpler solution I'm missing.
#I have a vector containing a sequence of numbers, with some duplicates and gaps,
#and I want to use its start and end points to create an analogous consecutive sequence.
original_sequence <- c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27,
28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42,
43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57,
58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72,
73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87,
88, 89, 90, 91, 92, 93, 94, 95, 96, 98, 98, 99, 100, 101,
102, 103, 104, 105, 106, 107, 108, 109, 110)
## unsuccessful attempt #1
original_sequence %>%
range() %>%
seq()
[1] 1 2 ## this result is equivalent to the output of `seq(2)`,
## but what I want is to compute `seq(1 ,110)`.
## unsuccessful attempt #2
original_sequence %>%
range() %>%
seq(.[1]), .[2])
Error: unexpected ',' in:
" range() %>%
seq(.[1]),"
## attempt #3: somewhat successful but I wonder whether there's a better way
original_sequence %>%
range() %>%
sapply(., seq)
[[1]]
[1] 1
[[2]]
[1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38
[39] 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76
[77] 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110
Bottom line -- I was able to do it with sapply
but I hope to figure out a solution in the spirit of my second attempt, because it's more handy to know a universal way to cherry-pick the specific vector elements you want to pass to the next function's arguments.
One way would be to use {}
and pass input arguments to seq
library(dplyr)
original_sequence %>%
range() %>%
{seq(.[[1]], .[2])}
#[1] 1 2 3 4 5 6 7 8 9 10 11 12......
Or we can mix it with base R do.call
original_sequence %>% range() %>% {do.call(seq, as.list(.))}
Or as @Ozan147 mentioned if your sequence always starts with 1 we can use max
original_sequence %>% max %>% seq