Provides a default method for rescale and rescale_mid #105
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The idea behind r-lib#74 and r-lib#75 was to use an S3 method so we never coerced to numeric unless we had to. The aim was to prevent future cases similar to the integer64 one where the coercion to numeric implies a loss of precision. Reality is that there are many more numeric types out there that do not inherit from the numeric class (like the dist object mentioned in r-lib#102), compared to the number of cases similar to integer64, where the numeric coercion is wrong. So there is a trade-off: - Not providing the `default` methods has the advantage that we only rescale the classes that we know can be rescaled, and the disadvantage that we get issues like r-lib#102 when we find a new object. This is what was implemented in r-lib#75 - Providing `rescale.default` and `rescale_mid.default` has the advantage of catching all the numeric-like types that do not inherit the numeric class (such as the dist object) and working as expected. However, we risk to deliver wrong results without an error if a case similar to integer64 appeared. This is what this commit implements.
This reverts commit cfabfae.
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Hi @dpseidel Thanks for your time working on the scales package and for reviewing this pull requests. Here is the support for Please tell me if there is anything else to be done on my end 😃 |
hadley
approved these changes
Jun 9, 2018
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In #74 and #75 we used a generic S3 method for
rescaleandrescale_mid. The aim was to handle more types of objects (POSIXt objects...) and to prevent errors like the loss of precision that happened when coercinginteger64tonumeric.While that PR fixed the support for POSIXt types, it also brought issue #102.
There are many numeric types out there that do not inherit from the numeric
class (like the
distobject mentioned in #102), compared to the number of cases similar to integer64, where the numeric coercion is wrong.So there is a trade-off:
Not providing the
defaultmethod inrescaleandrescale_midhas the advantage that we only rescale the classes that we know can be rescaled, and the disadvantage that we get issues like rescale stopped working with dist objects #102 when we find a new object. This approach is the current one and it was implemented in rescale() works with Date, POSIXct and POSIXlt objects. #75Providing
rescale.defaultandrescale_mid.defaulthas the advantage of catching all the numeric-like types that do not inherit the numeric class (such as the dist object) and working as expected. However, we risk to deliver wrong results without an error if a case similar to integer64 appeared. This is what this pull request follows.The changes of getting more issues like #102 are much higher than getting issues like the loss of precision in integer64 objects, so in my opinion this pull request makes sense.