# [R] Improvement: function cut

Leonard Mada |eo@m@d@ @end|ng |rom @yon|c@eu
Sat Sep 18 14:28:51 CEST 2021

```Hello Andrew,

I add this info as a completion (so other users can get a better
understanding):

If we want to perform a survival analysis, than the interval should be
closed to the right, but we should include also the first time point (as
per Intention-to-Treat):

[0, 4](4, 8](8, 12](12, 16]

[0, 4](4, 8](8, 12](12, 16](16, 20]

So the series is extendible to the right without any errors!

But the 1st interval (which is the same in both series) is different
from the other intervals: [0, 4].

I feel that this should have been the default behaviour for cut().

Note:

I was induced to think about a different situation in my previous
message, as you constructed open intervals on the right, and also
extended to the right. But survival analysis should be as described in
this mail and should probably be the default.

Sincerely,

Leonard

On 9/18/2021 1:29 AM, Andrew Simmons wrote:
> I disagree, I don't really think it's too long or ugly, but if you
> think it is, you could abbreviate it as 'i'.
>
>
> x <- 0:20
> breaks1 <- seq.int <http://seq.int>(0, 16, 4)
> breaks2 <- seq.int <http://seq.int>(0, 20, 4)
> data.frame(
>     cut(x, breaks1, right = FALSE, i = TRUE),
>     cut(x, breaks2, right = FALSE, i = TRUE),
>     check.names = FALSE
> )
>
>
> I hope this helps.
>
> On Fri, Sep 17, 2021 at 6:26 PM Leonard Mada <leo.mada using syonic.eu
>
>     Hello Andrew,
>
>
>     But "cut" generates factors. In most cases with real data one
>     expects to have also the ends of the interval: the argument
>     "include.lowest" is both ugly and too long.
>
>     [The test-code on the ftable thread contains this error! I have
>     run through this error a couple of times.]
>
>
>     The only real situation that I can imagine to be problematic:
>
>     - if the interval goes to +Inf (or -Inf): I do not know if there
>     would be any effects when including +Inf (or -Inf).
>
>
>     Leonard
>
>
>     On 9/18/2021 1:14 AM, Andrew Simmons wrote:
>>     While it is not explicitly mentioned anywhere in the
>>     documentation for .bincode, I suspect 'include.lowest = FALSE' is
>>     the default to keep the definitions of the bins consistent. For
>>     example:
>>
>>
>>     x <- 0:20
>>     breaks1 <- seq.int <http://seq.int>(0, 16, 4)
>>     breaks2 <- seq.int <http://seq.int>(0, 20, 4)
>>     cbind(
>>         .bincode(x, breaks1, right = FALSE, include.lowest = TRUE),
>>         .bincode(x, breaks2, right = FALSE, include.lowest = TRUE)
>>     )
>>
>>
>>     by having 'include.lowest = TRUE' with different ends, you can
>>     get inconsistent behaviour. While this probably wouldn't be an
>>     issue with 'real' data, this would seem like something you'd want
>>     to avoid by default. The definitions of the bins are
>>
>>
>>     [0, 4)
>>     [4, 8)
>>     [8, 12)
>>     [12, 16]
>>
>>
>>     and
>>
>>
>>     [0, 4)
>>     [4, 8)
>>     [8, 12)
>>     [12, 16)
>>     [16, 20]
>>
>>
>>     so you can see where the inconsistent behaviour comes from. You
>>     might be able to get R-core to add argument 'warn', but probably
>>     not to change the default of 'include.lowest'. I hope this helps
>>
>>
>>     On Fri, Sep 17, 2021 at 6:01 PM Leonard Mada <leo.mada using syonic.eu
>>
>>         Thank you Andrew.
>>
>>
>>         Is there any reason not to make: include.lowest = TRUE the
>>         default?
>>
>>
>>         Regarding the NA:
>>
>>         The user still has to suspect that some values were not
>>         included and run that test.
>>
>>
>>         Leonard
>>
>>
>>         On 9/18/2021 12:53 AM, Andrew Simmons wrote:
>>>         Regarding your first point, argument 'include.lowest'
>>>         already handles this specific case, see ?.bincode
>>>
>>>         Your second point, maybe it could be helpful, but since both
>>>         'cut.default' and '.bincode' return NA if a value isn't
>>>         within a bin, you could make something like this on your own.
>>>         Might be worth pitching to R-bugs on the wishlist.
>>>
>>>
>>>
>>>         On Fri, Sep 17, 2021, 17:45 Leonard Mada via R-help
>>>         <r-help using r-project.org <mailto:r-help using r-project.org>> wrote:
>>>
>>>             Hello List members,
>>>
>>>
>>>             the following improvements would be useful for function
>>>             cut (and .bincode):
>>>
>>>
>>>             1.) Argument: Include extremes
>>>             extremes = TRUE
>>>             if(right == FALSE) {
>>>                 # include also right for last interval;
>>>             } else {
>>>                 # include also left for first interval;
>>>             }
>>>
>>>
>>>             2.) Argument: warn = TRUE
>>>
>>>             Warn if any values are not included in the intervals.
>>>
>>>
>>>             Motivation:
>>>             - reduce risk of errors when using function cut();
>>>
>>>
>>>             Sincerely,
>>>
>>>
>>>             Leonard
>>>
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