On Jan 22, 2015, at 21:54, Guido van Rossum <guido@python.org> wrote:
I'd use an example with round numbers. "For example, to set a tolerance of 5%, pass tol=0.05. The default tolerance is 1e-8."
Hard to beat that for simplicity. +1 on this wording or something similar instead of the current abstract version.
On Thursday, January 22, 2015, Chris Barker <chris.barker@noaa.gov> wrote:
Andrew,
I totally agree that it's not going to be that clear to folks -- but I'm as stumped as you as to how to make it clear without getting really wordy.
Also, I think the percent error use case is infrequent, more likely would be that a relative tolerance of 1e-8 means that the numbers are the same to within about 8 significant decimal figures. After all, not many people think in terms of 0.0000001%
Suggestions gladly accepted!
-Chris
On Thu, Jan 22, 2015 at 7:30 PM, Andrew Barnert <abarnert@yahoo.com> wrote:
Overall I like it, but I'm not sure the help on the tol parameter is clear enough for people who don't already know what they want--in other words, the very people this function should be helping.
In my experience, novices understand relative tolerance immediately if you put it in terms of "within X% of expected", but don't always understand it if you put it in terms of "within X * expected" or, worse, "relative to the magnitude of the expected value". Just using % in there somewhere makes people get the concept.
Unfortunately, since the API doesn't actually use a percentage--and shouldn't--I'm not sure how to get this across in a one-liner in the help. You can always add something like "(e.g., a relative tolerance of .005 means that the actual value must be within 0.5% of the expected value)", but that's way too verbose.
(Also, I should note that the people I've explained this to have mostly been people with a US 1960-1990-style basic math education; I can't be sure that people who learned in another country, or in the post-post-new-math era in the US, etc. will respond the same way, although I do have a bit of anecdotal evidence from helping a few people on forums like StackOverflow that seems to imply they do.)
Sent from a random iPhone
On Jan 22, 2015, at 16:40, Chris Barker <chris.barker@noaa.gov> wrote:
is the relative tolerance -- it is the amount of error allowed, relative to the magnitude of the expected value.
--
Christopher Barker, Ph.D. Oceanographer
Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception
Chris.Barker@noaa.gov
-- --Guido van Rossum (on iPad)