Isn’t that the correct outcome? The user can change the number of digits if
they want to see small values…
--
Change your thoughts and you change the world.
--Dr. Norman Vincent Peale
> On Dec 17, 2023, at 12:11 AM, Steve Martin <stevemartin...@gmail.com> wrote:
>
> Zapping a vector of small numbers to zero would cause problems when
> printing the results of summary(). For example, if
> zapsmall(c(2.220446e-16, ..., 2.220446e-16)) == c(0, ..., 0) then
> print(summary(2.220446e-16), digits = 7) would print
> Min. 1st Qu. Median Mean 3rd Qu. Max.
> 0 0 0 0 0 0
>
> The same problem can also appear when printing the results of
> summary.glm() with show.residuals = TRUE if there's little dispersion
> in the residuals.
>
> Steve
>
>> On Sat, 16 Dec 2023 at 17:34, Gregory Warnes <g...@warnes.net> wrote:
>>
>> I was quite suprised to discover that applying `zapsmall` to a scalar value
>> has no apparent effect. For example:
>>
>>> y <- 2.220446e-16
>>> zapsmall(y,)
>> [1] 2.2204e-16
>>
>> I was expecting zapsmall(x)` to act like
>>
>>> round(y, digits=getOption('digits'))
>> [1] 0
>>
>> Looking at the current source code, indicates that `zapsmall` is expecting a
>> vector:
>>
>> zapsmall <-
>> function (x, digits = getOption("digits"))
>> {
>> if (length(digits) == 0L)
>> stop("invalid 'digits'")
>> if (all(ina <- is.na(x)))
>> return(x)
>> mx <- max(abs(x[!ina]))
>> round(x, digits = if (mx > 0) max(0L, digits - as.numeric(log10(mx)))
>> else digits)
>> }
>>
>> If `x` is a non-zero scalar, zapsmall will never perform rounding.
>>
>> The man page simply states:
>> zapsmall determines a digits argument dr for calling round(x, digits = dr)
>> such that values close to zero (compared with the maximal absolute value)
>> are ‘zapped’, i.e., replaced by 0.
>>
>> and doesn’t provide any details about how ‘close to zero’ is defined.
>>
>> Perhaps handling the special when `x` is a scalar (or only contains a single
>> non-NA value) would make sense:
>>
>> zapsmall <-
>> function (x, digits = getOption("digits"))
>> {
>> if (length(digits) == 0L)
>> stop("invalid 'digits'")
>> if (all(ina <- is.na(x)))
>> return(x)
>> mx <- max(abs(x[!ina]))
>> round(x, digits = if (mx > 0 && (length(x)-sum(ina))>1 ) max(0L, digits -
>> as.numeric(log10(mx))) else digits)
>> }
>>
>> Yielding:
>>
>>> y <- 2.220446e-16
>>> zapsmall(y)
>> [1] 0
>>
>> Another edge case would be when all of the non-na values are the same:
>>
>>> y <- 2.220446e-16
>>> zapsmall(c(y,y))
>> [1] 2.220446e-16 2.220446e-16
>>
>> Thoughts?
>>
>>
>> Gregory R. Warnes, Ph.D.
>> g...@warnes.net
>> Eternity is a long time, take a friend!
>>
>>
>>
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>>
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