Pipe/dplyr friendly way to filter non zero elements of a vector

Question

Surprisingly I am not finding an answer to this easy question. I need a pipe-friendly way to count the number of non-zero elements in a vector.

Without piping:

v <- c(1.1,2.2,0,0)
length(which(v != 0))

When I try to do this with pipes I get an error

v %>% which(. != 0) %>% length
Error in which(., . != 0) : argument to 'which' is not logical

A dplyr solution would also help

Related, more general post: [Using the %>% pipe, and dot (.) notation](https://stackoverflow.com/questions/42385010/using-the-pipe-and-dot-notation) — Henrik, May 19 '20 at 17:07

Ian Campbell · Accepted Answer · 2020-05-19T17:06:28.827

7

Here are some different options:

First, we can use {} with your original form:

v %>% {which(. != 0)} %>% length
#[1] 2

Or we could use {} to allow us to repeat .:

v %>% {.[. != 0]} %>% length
#[1] 2

Or we could use subset from Base R:

v %>% subset(. != 0) %>% length
#[1] 2

edited May 19 '20 at 17:06

answered May 19 '20 at 16:56

Ian Campbell

tmfmnk · Answer 2 · 2020-05-19T17:07:25.453

2

One way using magrittr could be:

v %>%
 equals(0) %>%
 not() %>%
 sum()

[1] 2

edited May 19 '20 at 17:07

answered May 19 '20 at 17:02

tmfmnk

I didn't realize there were all these functions in `help("extract","magrittr")`. Thanks for the introduction. – Ian Campbell May 19 '20 at 17:12

score 1 · Answer 3 · answered May 19 '20 at 17:38

1

We can convert to tibble and filter

library(dplyr)
tibble(v) %>% 
  filter(v != 0) %>%
  nrow
#[1] 2

answered May 19 '20 at 17:38

akrun

3 Answers3