1. Forum
  2. Usenet
  3. COMP.SOFT-SYS.MATH.MAPLE

  • Plotting polynomials to hard for Maple?

    From Peter Luschny@21:1/5 to All on Mon Oct 23 14:36:08 2017
    plot(5*x^4-20*x^3+30*x^2-20*x+5, x=0..1);

    https://imgur.com/a/UMVI2

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From William Unruh@21:1/5 to Peter Luschny on Tue Oct 24 03:59:52 2017
    On 2017-10-23, Peter Luschny <peter.luschny@gmail.com> wrote:
    plot(5*x^4-20*x^3+30*x^2-20*x+5, x=0..1);

    https://imgur.com/a/UMVI2

    Well it is a correct plot.
    Which version of Maple? Mine has no trouble (it is Maple 9.5)

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From acer@21:1/5 to Peter Luschny on Tue Oct 24 00:07:55 2017
    On Monday, October 23, 2017 at 5:36:09 PM UTC-4, Peter Luschny wrote:
    plot(5*x^4-20*x^3+30*x^2-20*x+5, x=0..1);

    https://imgur.com/a/UMVI2

    As usual Peter does not mention which Maple version he's using here. This makes it awkward to figure out the nature of the problem. I'll make a guess.

    When the 2-D plot option `smartview` was introduced in Maple 16 it had a few problems. This option was `true` by default, one of the problems is that it could be too conservative in estimating that the curve had become steep enough to warrant limiting
    the displayed range.

    If one executes Peter's example using, say, Maple 16.02 then the vertical range displayed goes from 0.0 only to about 2.5 (very much like in his linked image).

    Specifying the option smartview=false explicitly resolves the problem in Maple 16.02. Eg.

    plot(5*x^4-20*x^3+30*x^2-20*x+5, x=0..1, smartview=false);

    Improvements to the underlying scheme already make Peter's example show the full range from 0.0 to 5.0 in Maple 17.02 and onwards.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Peter Luschny@21:1/5 to All on Thu Oct 26 02:39:30 2017
    Am Dienstag, 24. Oktober 2017 06:00:02 UTC+2 schrieb William Unruh:
    On 2017-10-23, Peter Luschny wrote:
    plot(5*x^4-20*x^3+30*x^2-20*x+5, x=0..1);
    https://imgur.com/a/UMVI2

    Well it is a correct plot.

    Is it? No, I expect that the y-axis shows up to 5
    which is the value of p(0).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Peter Luschny@21:1/5 to All on Thu Oct 26 02:50:07 2017
    Am Dienstag, 24. Oktober 2017 09:07:55 UTC+2 schrieb acer:
    On Monday, October 23, 2017 at 5:36:09 PM UTC-4, Peter Luschny wrote:
    plot(5*x^4-20*x^3+30*x^2-20*x+5, x=0..1);
    https://imgur.com/a/UMVI2

    As usual Peter does not mention which Maple version he's using here.

    Because it does not matter.

    There are many many different versions out there and the purpose of
    my posts is to alert Maple users so they can check if their version
    is correct or if they have to expect this or similar bugs.

    Improvements to the underlying scheme already make Peter's example
    show the full range from 0.0 to 5.0 in Maple 17.02 and onwards.

    Ha ha, try it with Maple V, Release 5, about 1998.
    So much for the "improvements" which "already" show
    things right "in Maple 17.02 and onwards".

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From William Unruh@21:1/5 to Peter Luschny on Thu Oct 26 16:12:29 2017
    On 2017-10-26, Peter Luschny <peter.luschny@gmail.com> wrote:
    Am Dienstag, 24. Oktober 2017 09:07:55 UTC+2 schrieb acer:
    On Monday, October 23, 2017 at 5:36:09 PM UTC-4, Peter Luschny wrote:
    plot(5*x^4-20*x^3+30*x^2-20*x+5, x=0..1);
    https://imgur.com/a/UMVI2

    As usual Peter does not mention which Maple version he's using here.

    Because it does not matter.

    There are many many different versions out there and the purpose of
    my posts is to alert Maple users so they can check if their version
    is correct or if they have to expect this or similar bugs.

    No. You said that Maple does this. It does not. Your particular version
    may, and as such you should tell us which version you use.


    Improvements to the underlying scheme already make Peter's example
    show the full range from 0.0 to 5.0 in Maple 17.02 and onwards.

    Ha ha, try it with Maple V, Release 5, about 1998.
    So much for the "improvements" which "already" show
    things right "in Maple 17.02 and onwards".

    You mean it plots it differently? So it is not Maple which does it
    incorrectly but some specific version? So why "it does not matter" when
    you contradict that in the same post?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Juergen Barsuhn@21:1/5 to All on Wed Nov 1 16:12:52 2017
    Am 23.10.2017 um 23:36 schrieb Peter Luschny:
    plot(5*x^4-20*x^3+30*x^2-20*x+5, x=0..1);

    https://imgur.com/a/UMVI2


    I would expect, that the range of ordinates is automatically adjusted to
    the actual range of values of the functional term. Maybe you have fixed
    the y-range by a preseding command. Nevertheless, you can enforce an
    adequte range by
    plot(5*x^4-20*x^3+30*x^2-20*x+5, x=0..1,0..5);

    Your term is just 5*(x-1)^4, thus a look on a larger portion of the 4th
    order parabola might be of interest:
    plot(5*x^4-20*x^3+30*x^2-20*x+5, x=0..2,-1..6);

    Regards, Jurgen

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)