Iterator that filters elements where corresponding selector is false.

Constructs an iterator that filters elements from iterable returning only those for which the corresponding element from selectors is TRUE.

Usage

i_mask(object, selectors)

Arguments

object: an iterable object
selectors: an iterable that determines whether the corresponding element in object is returned.

Value

iterator object

Details

The iterator stops when either object or selectors has been exhausted.

Examples

# Filters out odd numbers and retains only even numbers
n <- 10
selectors <- rep(c(FALSE, TRUE), n)
it <- i_mask(seq_len(n), selectors)
as.list(it)
#> [[1]]
#> [1] 2
#> 
#> [[2]]
#> [1] 4
#> 
#> [[3]]
#> [1] 6
#> 
#> [[4]]
#> [1] 8
#> 
#> [[5]]
#> [1] 10
#> 

# Similar idea here but anonymous function is used to filter out even
# numbers
n <- 10
it2 <- i_mask(seq_len(10), rep(c(TRUE, FALSE), n))
as.list(it2)
#> [[1]]
#> [1] 1
#> 
#> [[2]]
#> [1] 3
#> 
#> [[3]]
#> [1] 5
#> 
#> [[4]]
#> [1] 7
#> 
#> [[5]]
#> [1] 9
#> 

it3 <- i_mask(letters, letters %in% c('a', 'e', 'i', 'o', 'u'))
as.list(it3)
#> [[1]]
#> [1] "a"
#> 
#> [[2]]
#> [1] "e"
#> 
#> [[3]]
#> [1] "i"
#> 
#> [[4]]
#> [1] "o"
#> 
#> [[5]]
#> [1] "u"
#>