00:43:02 Gus Lipkin: I think I found the definition for `mean`
An R call goes to *a which then calls the C function *b
*a: https://github.com/wch/r-source/blob/trunk/src/library/base/R/mean.R
*b: https://github.com/wch/r-source/blob/trunk/src/library/stats/src/cov.c#L207
It looks like the second pass only happens if `R_FINITE(mean_from_first_pass)` which tries to call `isfinite` from C++ and if it’s not there, it’ll make sure it is a number and is not positive or negative infinity.
00:49:55 Gus Lipkin: I feel bad for dropping in on the last chapter and getting Collin’s thanks 😅 I wish I’d joined sooner.