R help - Jun 2021 - How to spot/stop making the same mistake

In my code, instead of 't', I name a vector of indices with a meaningful
name, such as idxV, to make it obvious.

Alternatively, a minor change in your style would be to replace your
definition of t by

t <- as.logical(c(1,1,1,0,0))

HTH,
Eric


On Wed, Jun 23, 2021 at 6:11 PM Phillips Rogfield <thebudget72 at
gmail.com>
wrote:
> I make the same mistake all over again.
>
> In particular, suppose we have:
>
> a = c(1,2,3,4,5)
>
> and a variable that equals 1 for the elements I want to select:
>
> t = c(1,1,1,0,0)
>
> To select the first 3 elements.
>
> The problem is that
>
> a[t]
>
> would repeat the first element 3 times .....
>
> I have to either convert `t` to boolean:
>
> a[t==1]
>
> Or use `which`
>
> a[which(t==1)]
>
> How can I "spot" this error?
>
> It often happens in long scripts.
>
> Do I have to check the type each time?
>
> Do you have any suggestions?
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

Just as a way to save a bit of typing, instead of
> as.logical(0:4)
[1] FALSE  TRUE  TRUE  TRUE  TRUE
> !!(0:4)
[1] FALSE  TRUE  TRUE  TRUE  TRUE

DO NOTE that the parentheses in the second expression should never be
omitted, a possible reason to prefer the as.logical() construction.
Also note that !!  "acts [only] on raw, logical and number-like
vectors,"
whereas as.logical() is more general. e.g. (from ?logical):
> charvec <- c("FALSE", "F", "False",
"false",    "fAlse", "0",
+              "TRUE",  "T", "True", 
"true",     "tRue",  "1")
> as.logical(charvec)
 [1] FALSE FALSE FALSE FALSE    NA    NA  TRUE  TRUE  TRUE  TRUE    NA   
NA
> !!charvec
Error in !charvec : invalid argument type


Cheers,
Bert

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Wed, Jun 23, 2021 at 8:31 AM Eric Berger <ericjberger at gmail.com>
wrote:
> In my code, instead of 't', I name a vector of indices with a
meaningful
> name, such as idxV, to make it obvious.
>
> Alternatively, a minor change in your style would be to replace your
> definition of t by
>
> t <- as.logical(c(1,1,1,0,0))
>
> HTH,
> Eric
>
>
> On Wed, Jun 23, 2021 at 6:11 PM Phillips Rogfield <thebudget72 at
gmail.com>
> wrote:
>
> > I make the same mistake all over again.
> >
> > In particular, suppose we have:
> >
> > a = c(1,2,3,4,5)
> >
> > and a variable that equals 1 for the elements I want to select:
> >
> > t = c(1,1,1,0,0)
> >
> > To select the first 3 elements.
> >
> > The problem is that
> >
> > a[t]
> >
> > would repeat the first element 3 times .....
> >
> > I have to either convert `t` to boolean:
> >
> > a[t==1]
> >
> > Or use `which`
> >
> > a[which(t==1)]
> >
> > How can I "spot" this error?
> >
> > It often happens in long scripts.
> >
> > Do I have to check the type each time?
> >
> > Do you have any suggestions?
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]