Using Filter(Negate(is.na), x) on a list results in unexpected behaviour

Consider

l1 <- list("a", NA, 1:3, NA)

l2 <- list("a", NULL, 1:3, NULL)

Why does Filter(Negate(is.na), l1) not work, while Filter(Negate(is.null), l2) does work as expected (it returns all elements of l2 which are not NULL)?

The helpfile for ?Filter says

...Note that possible NA values are currently always taken as false; control over NA handling may be added in the future.

I still dont really understand the behaviour.

asked Nov 13 '18 at 8:46

Manuel R

1,39211229

add a comment |

Consider

l1 <- list("a", NA, 1:3, NA)

l2 <- list("a", NULL, 1:3, NULL)

Why does Filter(Negate(is.na), l1) not work, while Filter(Negate(is.null), l2) does work as expected (it returns all elements of l2 which are not NULL)?

The helpfile for ?Filter says

...Note that possible NA values are currently always taken as false; control over NA handling may be added in the future.

I still dont really understand the behaviour.

asked Nov 13 '18 at 8:46

Manuel R

1,39211229

add a comment |

Consider

l1 <- list("a", NA, 1:3, NA)

l2 <- list("a", NULL, 1:3, NULL)

Why does Filter(Negate(is.na), l1) not work, while Filter(Negate(is.null), l2) does work as expected (it returns all elements of l2 which are not NULL)?

The helpfile for ?Filter says

...Note that possible NA values are currently always taken as false; control over NA handling may be added in the future.

I still dont really understand the behaviour.

asked Nov 13 '18 at 8:46

Manuel R

1,39211229

Consider

l1 <- list("a", NA, 1:3, NA)

l2 <- list("a", NULL, 1:3, NULL)

Why does Filter(Negate(is.na), l1) not work, while Filter(Negate(is.null), l2) does work as expected (it returns all elements of l2 which are not NULL)?

The helpfile for ?Filter says

...Note that possible NA values are currently always taken as false; control over NA handling may be added in the future.

I still dont really understand the behaviour.

asked Nov 13 '18 at 8:46

Manuel R

1,39211229

asked Nov 13 '18 at 8:46

Manuel R

1,39211229

asked Nov 13 '18 at 8:46

Manuel R

1,39211229

asked Nov 13 '18 at 8:46

Manuel R

1,39211229

asked Nov 13 '18 at 8:46

Manuel R

1,39211229

add a comment |

1 Answer
1

active

oldest

votes

is.na returns a vector for each element of the list; you want anyNA (or perhaps exactlyNA as defined below):

l1 <- list("a", NA, 1:3, NA)

l2 <- list("a", NULL, 1:3, NULL) 

Filter(Negate(is.na), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

#> 

#> [[3]]

#> [1] NA

#> 

#> [[4]]

#> NULL

Filter(Negate(anyNA), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

exactlyNA <- function(x) identical(x, NA)

Filter(Negate(exactlyNA), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

^{Created on 2018-11-13 by the reprex package (v0.2.1)}

Your first example effectively tries to select the 1st, 3rd, 4th, and 5th elements of your list. Nothing to do with NA.

edited Nov 13 '18 at 9:00

answered Nov 13 '18 at 8:56

Hugh

7,13443569

Nice thank you!
– Manuel R
Nov 13 '18 at 9:00

add a comment |

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1 Answer
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1 Answer
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is.na returns a vector for each element of the list; you want anyNA (or perhaps exactlyNA as defined below):

l1 <- list("a", NA, 1:3, NA)

l2 <- list("a", NULL, 1:3, NULL) 

Filter(Negate(is.na), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

#> 

#> [[3]]

#> [1] NA

#> 

#> [[4]]

#> NULL

Filter(Negate(anyNA), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

exactlyNA <- function(x) identical(x, NA)

Filter(Negate(exactlyNA), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

^{Created on 2018-11-13 by the reprex package (v0.2.1)}

Your first example effectively tries to select the 1st, 3rd, 4th, and 5th elements of your list. Nothing to do with NA.

edited Nov 13 '18 at 9:00

answered Nov 13 '18 at 8:56

Hugh

7,13443569

Nice thank you!
– Manuel R
Nov 13 '18 at 9:00

add a comment |

is.na returns a vector for each element of the list; you want anyNA (or perhaps exactlyNA as defined below):

l1 <- list("a", NA, 1:3, NA)

l2 <- list("a", NULL, 1:3, NULL) 

Filter(Negate(is.na), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

#> 

#> [[3]]

#> [1] NA

#> 

#> [[4]]

#> NULL

Filter(Negate(anyNA), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

exactlyNA <- function(x) identical(x, NA)

Filter(Negate(exactlyNA), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

^{Created on 2018-11-13 by the reprex package (v0.2.1)}

Your first example effectively tries to select the 1st, 3rd, 4th, and 5th elements of your list. Nothing to do with NA.

edited Nov 13 '18 at 9:00

answered Nov 13 '18 at 8:56

Hugh

7,13443569

Nice thank you!
– Manuel R
Nov 13 '18 at 9:00

add a comment |

is.na returns a vector for each element of the list; you want anyNA (or perhaps exactlyNA as defined below):

l1 <- list("a", NA, 1:3, NA)

l2 <- list("a", NULL, 1:3, NULL) 

Filter(Negate(is.na), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

#> 

#> [[3]]

#> [1] NA

#> 

#> [[4]]

#> NULL

Filter(Negate(anyNA), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

exactlyNA <- function(x) identical(x, NA)

Filter(Negate(exactlyNA), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

^{Created on 2018-11-13 by the reprex package (v0.2.1)}

Your first example effectively tries to select the 1st, 3rd, 4th, and 5th elements of your list. Nothing to do with NA.

edited Nov 13 '18 at 9:00

answered Nov 13 '18 at 8:56

Hugh

7,13443569

is.na returns a vector for each element of the list; you want anyNA (or perhaps exactlyNA as defined below):

l1 <- list("a", NA, 1:3, NA)

l2 <- list("a", NULL, 1:3, NULL) 

Filter(Negate(is.na), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

#> 

#> [[3]]

#> [1] NA

#> 

#> [[4]]

#> NULL

Filter(Negate(anyNA), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

exactlyNA <- function(x) identical(x, NA)

Filter(Negate(exactlyNA), l1)

#> [[1]]

#> [1] "a"

#> 

#> [[2]]

#> [1] 1 2 3

^{Created on 2018-11-13 by the reprex package (v0.2.1)}

Your first example effectively tries to select the 1st, 3rd, 4th, and 5th elements of your list. Nothing to do with NA.

edited Nov 13 '18 at 9:00

answered Nov 13 '18 at 8:56

Hugh

7,13443569

edited Nov 13 '18 at 9:00

answered Nov 13 '18 at 8:56

Hugh

7,13443569

answered Nov 13 '18 at 8:56

Hugh

7,13443569

answered Nov 13 '18 at 8:56

Hugh

7,13443569

Nice thank you!
– Manuel R
Nov 13 '18 at 9:00

add a comment |

Nice thank you!
– Manuel R
Nov 13 '18 at 9:00

Nice thank you!
– Manuel R
Nov 13 '18 at 9:00

add a comment |

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