[Rd] Is this a bug in `[`?

[Rui Barradas]

Hello,

Maybe I am not understanding how negative indexing works but

1) This is right.

(1:10)[-1]
#[1]  2  3  4  5  6  7  8  9 10

2) Are these right? They are at least surprising to me.

(1:10)[-0]
#integer(0)

(1:10)[-seq_len(0)]
#integer(0)


It was the last example that made me ask, seq_len(0) whould avoid an 
if/else or something similar.



Thanks in advance,

Rui Barradas

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[Rd] Puzzle or bug with matrix indexing

[David Hugh-Jones]

I'm not sure why this is happening:

tmp <- data.frame(
  a = letters[1:2],
  b=c(TRUE, FALSE),
  stringsAsFactors = FALSE
)
idx <- matrix(c(1, 2, 2, 2), 2, byrow = TRUE)
tmp[idx]

[1] " TRUE" "FALSE"

Notice there is a space before the TRUE: " TRUE".

This space isn't happening purely because of coercion:

c("blah", TRUE, FALSE)
[1] "blah"  "TRUE"  "FALSE"

No space.

Obviously:
as.logical(tmp[idx])
[1]NA FALSE

which is why I think this might be a bug.

David

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[Rd] typo in Ubuntu download page

[J C Nash]

In https://cran.r-project.org/bin/linux/ubuntu/

Administration and Maintances of R Packages
   ^^

Minor stuff, but if someone who can edit is on the page,
perhaps it can be changed to "Maintenance"

Best, JN

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Re: [Rd] Is this a bug in `[`?

[Iñaki Úcar]

El sáb., 4 ago. 2018 a las 15:32, Rui Barradas
() escribió:
>
> Hello,
>
> Maybe I am not understanding how negative indexing works but
>
> 1) This is right.
>
> (1:10)[-1]
> #[1]  2  3  4  5  6  7  8  9 10
>
> 2) Are these right? They are at least surprising to me.
>
> (1:10)[-0]
> #integer(0)
>
> (1:10)[-seq_len(0)]
> #integer(0)
>
>
> It was the last example that made me ask, seq_len(0) whould avoid an
> if/else or something similar.

I think it's ok, because there is no negative zero integer, so -0 is 0.

1.0/-0L # Inf
1.0/-0.0 # - Inf

And the same can be said for integer(0), which is the result of
seq_len(0): there is no negative empty integer.

Iñaki

>
>
> Thanks in advance,
>
> Rui Barradas
>
> __
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> https://stat.ethz.ch/mailman/listinfo/r-devel

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Re: [Rd] Is this a bug in `[`?

[Rui Barradas]

Às 15:51 de 04/08/2018, Iñaki Úcar escreveu:

El sáb., 4 ago. 2018 a las 15:32, Rui Barradas
() escribió:


Hello,

Maybe I am not understanding how negative indexing works but

1) This is right.

(1:10)[-1]
#[1]  2  3  4  5  6  7  8  9 10

2) Are these right? They are at least surprising to me.

(1:10)[-0]
#integer(0)

(1:10)[-seq_len(0)]
#integer(0)


It was the last example that made me ask, seq_len(0) whould avoid an
if/else or something similar.


I think it's ok, because there is no negative zero integer, so -0 is 0.


Ok, this makes sense, I should have thought about that.



1.0/-0L # Inf
1.0/-0.0 # - Inf

And the same can be said for integer(0), which is the result of
seq_len(0): there is no negative empty integer.


I'm not completely convinced about this one, though.
I would expect -seq_len(n) to remove the first n elements from the 
vector, therefore, when n == 0, it would remove none.


And integer(0) is not the same as 0.

(1:10)[-0] == (1:10)[0] == integer(0) # empty

(1:10)[-seq_len(0)] == (1:10)[-integer(0)]


And I have just reminded myself to run

identical(-integer(0), integer(0))

It returns TRUE so my intuition is wrong, R is right.
End of story.

Thanks for the help,

Rui Barradas



Iñaki




Thanks in advance,

Rui Barradas

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Re: [Rd] Puzzle or bug with matrix indexing

[Berry, Charles]

> On Aug 4, 2018, at 6:55 AM, David Hugh-Jones  wrote:
> 
> I'm not sure why this is happening:
> 
> tmp <- data.frame(
>  a = letters[1:2],
>  b=c(TRUE, FALSE),
>  stringsAsFactors = FALSE
> )
> idx <- matrix(c(1, 2, 2, 2), 2, byrow = TRUE)
> tmp[idx]
> 
> [1] " TRUE" "FALSE"
> 

>From ?"[.data.frame"

Extract.data.frame {base}
.
.
.
Matrix indexing (x[i] with a logical or a 2-column integer matrix i) using [ is 
not recommended. For extraction, x is first coerced to a matrix.

[...]

Thus, something like 

as.matrix(tmp)

happens converting every column to character. Dig deeper by reading

?matrix

and see the paragraph on `as.matrix' under `Details'.

HTH,

Chuck
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Re: [Rd] Puzzle or bug with matrix indexing

[David Hugh-Jones]

Yup, I worked it out in time... for future reference, as.matrix calls
`format` on logicals, converting them to the form seen.

On Sat, 4 Aug 2018 at 17:53, Berry, Charles  wrote:

>
>
> > On Aug 4, 2018, at 6:55 AM, David Hugh-Jones 
> wrote:
> >
> > I'm not sure why this is happening:
> >
> > tmp <- data.frame(
> >  a = letters[1:2],
> >  b=c(TRUE, FALSE),
> >  stringsAsFactors = FALSE
> > )
> > idx <- matrix(c(1, 2, 2, 2), 2, byrow = TRUE)
> > tmp[idx]
> >
> > [1] " TRUE" "FALSE"
> >
>
> From ?"[.data.frame"
>
> Extract.data.frame {base}
> .
> .
> .
> Matrix indexing (x[i] with a logical or a 2-column integer matrix i) using
> [ is not recommended. For extraction, x is first coerced to a matrix.
>
> [...]
>
> Thus, something like
>
> as.matrix(tmp)
>
> happens converting every column to character. Dig deeper by reading
>
> ?matrix
>
> and see the paragraph on `as.matrix' under `Details'.
>
> HTH,
>
> Chuck
>
-- 
Sent from Gmail Mobile

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Re: [Rd] Is this a bug in `[`?

[Kenny Bell]

This should more clearly illustrate the issue:

c(1, 2, 3, 4)[-seq_len(4)]
#> numeric(0)
c(1, 2, 3, 4)[-seq_len(3)]
#> [1] 4
c(1, 2, 3, 4)[-seq_len(2)]
#> [1] 3 4
c(1, 2, 3, 4)[-seq_len(1)]
#> [1] 2 3 4
c(1, 2, 3, 4)[-seq_len(0)]
#> numeric(0)
Created on 2018-08-05 by the reprex package (v0.2.0.9000).

On Sun, Aug 5, 2018 at 3:58 AM Rui Barradas  wrote:

>
>
> Às 15:51 de 04/08/2018, Iñaki Úcar escreveu:
> > El sáb., 4 ago. 2018 a las 15:32, Rui Barradas
> > () escribió:
> >>
> >> Hello,
> >>
> >> Maybe I am not understanding how negative indexing works but
> >>
> >> 1) This is right.
> >>
> >> (1:10)[-1]
> >> #[1]  2  3  4  5  6  7  8  9 10
> >>
> >> 2) Are these right? They are at least surprising to me.
> >>
> >> (1:10)[-0]
> >> #integer(0)
> >>
> >> (1:10)[-seq_len(0)]
> >> #integer(0)
> >>
> >>
> >> It was the last example that made me ask, seq_len(0) whould avoid an
> >> if/else or something similar.
> >
> > I think it's ok, because there is no negative zero integer, so -0 is 0.
>
> Ok, this makes sense, I should have thought about that.
>
> >
> > 1.0/-0L # Inf
> > 1.0/-0.0 # - Inf
> >
> > And the same can be said for integer(0), which is the result of
> > seq_len(0): there is no negative empty integer.
>
> I'm not completely convinced about this one, though.
> I would expect -seq_len(n) to remove the first n elements from the
> vector, therefore, when n == 0, it would remove none.
>
> And integer(0) is not the same as 0.
>
> (1:10)[-0] == (1:10)[0] == integer(0) # empty
>
> (1:10)[-seq_len(0)] == (1:10)[-integer(0)]
>
>
> And I have just reminded myself to run
>
> identical(-integer(0), integer(0))
>
> It returns TRUE so my intuition is wrong, R is right.
> End of story.
>
> Thanks for the help,
>
> Rui Barradas
>
> >
> > Iñaki
> >
> >>
> >>
> >> Thanks in advance,
> >>
> >> Rui Barradas
> >>
> >> __
> >> R-devel@r-project.org mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-devel
>
> __
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>

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Re: [Rd] Is this a bug in `[`?

[Rui Barradas]

Thanks.
This is exactly the doubt I had.

Rui Barradas

Às 05:26 de 05/08/2018, Kenny Bell escreveu:

This should more clearly illustrate the issue:

c(1, 2, 3, 4)[-seq_len(4)]
#> numeric(0)
c(1, 2, 3, 4)[-seq_len(3)]
#> [1] 4
c(1, 2, 3, 4)[-seq_len(2)]
#> [1] 3 4
c(1, 2, 3, 4)[-seq_len(1)]
#> [1] 2 3 4
c(1, 2, 3, 4)[-seq_len(0)]
#> numeric(0)
Created on 2018-08-05 by the reprex package (v0.2.0.9000).

On Sun, Aug 5, 2018 at 3:58 AM Rui Barradas > wrote:




Às 15:51 de 04/08/2018, Iñaki Úcar escreveu:
 > El sáb., 4 ago. 2018 a las 15:32, Rui Barradas
 > (mailto:ruipbarra...@sapo.pt>>) escribió:
 >>
 >> Hello,
 >>
 >> Maybe I am not understanding how negative indexing works but
 >>
 >> 1) This is right.
 >>
 >> (1:10)[-1]
 >> #[1]  2  3  4  5  6  7  8  9 10
 >>
 >> 2) Are these right? They are at least surprising to me.
 >>
 >> (1:10)[-0]
 >> #integer(0)
 >>
 >> (1:10)[-seq_len(0)]
 >> #integer(0)
 >>
 >>
 >> It was the last example that made me ask, seq_len(0) whould avoid an
 >> if/else or something similar.
 >
 > I think it's ok, because there is no negative zero integer, so -0
is 0.

Ok, this makes sense, I should have thought about that.

 >
 > 1.0/-0L # Inf
 > 1.0/-0.0 # - Inf
 >
 > And the same can be said for integer(0), which is the result of
 > seq_len(0): there is no negative empty integer.

I'm not completely convinced about this one, though.
I would expect -seq_len(n) to remove the first n elements from the
vector, therefore, when n == 0, it would remove none.

And integer(0) is not the same as 0.

(1:10)[-0] == (1:10)[0] == integer(0) # empty

(1:10)[-seq_len(0)] == (1:10)[-integer(0)]


And I have just reminded myself to run

identical(-integer(0), integer(0))

It returns TRUE so my intuition is wrong, R is right.
End of story.

Thanks for the help,

Rui Barradas

 >
 > Iñaki
 >
 >>
 >>
 >> Thanks in advance,
 >>
 >> Rui Barradas
 >>
 >> __
 >> R-devel@r-project.org  mailing list
 >> https://stat.ethz.ch/mailman/listinfo/r-devel

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