Re: Package statistics: tricdf (bug?)

On Tue, Jun 23, 2020 at 5:37 AM Evangelos Rozos <[email protected]> wrote:

> I think something is wrong with tricdf function (maybe triinv also).
>
>  >> tricdf (0.7, 0.5, 1.0, 0.9)
>
> ans =  0.16000
>
> The correct answer should be 0.2.
>
> MATLAB gives 0.2. This value can be also verified by the geometry of the
> pdf triangle with base from 0.5 to 1, and height 4 at 0.9. Then, the
> area of the triangle with base from 0.5 to 0.7 and height 2 (0.7 is in
> the middle of the 0.5 to 0.9 segment) is 0.2.
>
>
tricdf code has few problems.  For you reported problem this fix should
work:
<     area = (x(k_temp) - a).^2 * h;
---
>     area = (x(k_temp) - a).^2 * h / (c - a) / 2 ;
74c74
<     area = (b-x(k_temp)).^2 * h;
---
>     area = (b-x(k_temp)).^2 * h / (b - c) / 2 ;

A similar change should be done for the code segment that deals with the
case of
A,B, and C being arrays rather than scalar. I really do not understand the
intent of that code.
It requires the size of X, A, B, and C to be the same. That does not make
much sense to me.
I think A, B and C should be scalars. I do not think there is a compatible
matlab's function.

Dmitri.
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