On 6/15/21, Britt Anderson <britt.uwater...@gmail.com> wrote:
>
> I was starting to explore plot and I am getting a behavior I do not
> understand. plot doesn't seem to be able to figure out the bounds for
> something that seems pretty straight-forward. When I give bounds as an
> optional argument I don't see the line I expect to see. Can anyone provide
> me some pointers? I feel like I am just missing something conceptually and
> would appreciate some guidance. Here is some minimal code to demonstrate
> the problem. I get a plot square, but no line, and I can demonstrate that
> the function generates reasonable numbers for this range of inputs.
>
>
>
> #lang racket
> (require plot)
> (require math/distributions)
>
> (define (norm-prior mu)
> (lambda (sd)
> (lambda (ind)
> (* ind (flnormal-pdf mu sd ind #f)))))
>
> (define d ((norm-prior 0.5) 0.1))
>
> (plot (function d 0 1 #:y-min 0.0 #:y-max 2.0 #:samples 100))
>
> (map d (range 0.0 1.0 0.01))
>
This is tricky.
Plot is calling your function `d` with inputs like 0, 1/99, and 1. All
of those give contract errors --- try (d 0) for yourself.
But when a plot function throws an error, the library ignores the
problem & keeps trying to draw a picture.
To fix, I'd change `norm-prior` to make a flonum:
(define (norm-prior mu)
(lambda (sd)
(lambda (ind)
(* ind (flnormal-pdf mu sd (exact->inexact ind) #f)))))
[[ Maybe plot should check if a function renderer produces no output
and throw an error then. ]]
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