[R] NAs produced by integer overflow, but only some time ...
Stefan Th. Gries
@tgr|e@ @end|ng |rom gm@||@com
Wed May 9 16:58:19 CEST 2018
Before responding to Jeff's posting, let me reiterate my question: Why
does a function using m1*m1 produce an integer overflow, but m1^2 does
As for Jeff's 'response':
> a) Numeric values may be either integers (signed 32 bit) or double precision (53 bit mantissa).
> b) Double precision constants are numeric with no decoration (e.g. 61224). Integer constants have an L (e.g. 61224L).
> c) 61224*61224 > 2^31-1 so that answer cannot fit into an integer.
> d) Exponentiation is a floating point operation so the result of 61224L^2L is a floating point answer that CAN fit into the 53bit mantissa of a double precision value, so no overflow occurs.
Yes, that's all great and I knew that from
> e) Defining a function like yules.k1 and never showing how you called it does not constitute a reproducible example. To avoid such gaffes you can use the reprex package to confirm that the errors shown in your question are in fact reproducible.
Responding to a post and never seeing that the provided code does
actually show how I call the function does not constitute a useful
answer. To avoid such gaffes you can use your reading skills to
confirm that the perceived lack of a function call is in fact such a
lack. In addition, typing m1 <- 61224 makes the multiplication example
that I shows in the bottom part of the posting reproducible ...
> f) On this mailing list, the fact that you are using RStudio is at best irrelevant, and at worst off-topic. If you don't see problems running your reproducible example from R in the terminal then the question probably belongs in the RStudio support forum. This is another reason to use the reprex package to check your reproducibility (this works even if you invoke it from RStudio).
I did provide the information for the sake of comprehensiveness and I
did mention that the problem also showed up in the console; the whole
second part of the post was on that.
> g) Calling table on the result of table must be one of the more bizarre calculation sequences I have ever seen in R. I hope you are getting the answers you are expecting when you do use double precision numeric values. Also, using the prefix form of multiplication is unnecessarily obscure, and your use of the return function at the end of your function is redundant.
On this mailing list, your assessment of calculation sequences and
their comparison to others you have seen is at best irrelevant and at
worst off-topic since it doesn't answer the question. I didn't ask
(you or anyone) to grade my code and there are reasons why "*" and
return where used there as they are) but to answer the question why
m1*m1 returned an error and m1^2 does not.
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