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Re: Substract value from contour line to surface

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Am 18.09.2018 um 09:36 schrieb laterite@laposte.net:
> Le mardi 18 septembre 2018 07:47:00 UTC+2, Karl Ratzsch a écrit :
>> Am 18.09.2018 um 07:08 schrieb laterite@laposte.net:
>>> Le lundi 17 septembre 2018 22:25:51 UTC+2, Hans-Bernhard Bröker a écrit :
>>>> Am 17.09.2018 um 17:17 schrieb laterite@laposte.net:
>>>>> Hi,
>>>>>
>>>>> I have an analytical 2D function G(x,y) and a .dat file giving me the x0,y0 points solution of the equation G(x0,y0)=0 in a .dat file.
>>>>
>>>> There is not really such a thing as "the" points that fulfill that 
>>>> criterion --- at least none where that whole set fits into a finite-size 
>>>> data file.  So let's say you have some subset of that in a file.
>>>>
>>>>> Now, I would like to plot the surface of the function G(x,y0)-G(x0,y0).
>>>>
>>>> How isn't that the exact same surface as G(x,y) itself?  You've just 
>>>> renamed the second independent variable and subtracted a constant zero!
>>>
>>>
>>> Sorry, my bad, I made a mistake in my explanation :
>>>
>>> I have an analytical 2D function G(x,y) and a .dat file giving me a subset of x0,y0 points solution of the equation dG/dx|_y=0 in a .dat file.
>>>
>>> And no I want to plot G(x,y0)-G(x0,y0)
>>>
>>
>> What are x0 and y0, i.e. which pair from your solution data file do you
>> want to use for this plot?
>>
>> Or do you want the set of all those curves?
> 
> I want to plot the surface of those.
> 

I still don't follow completely, but if I understand correctly, the
basic problem is you can't easily mix a data plot in direction x with a
function plot in direction y.

It might work like following (you'll have to figure out the exact syntax
yourself, no time now)

- the special file name "++" generates a grid of two independent
variables which are varied over the set range

- you could write your y0 values into an array from which you read them
by using y as the indexing variable (set y sampling accordingly).

- the splot command would look somethign like following
   splot sample [x=-10:10] [y=1:14] "++" \
   using 1:(y0[t(y)]):G(x,y0[t(y)])-G(x0,y0[t(y)])

where t(y) = trunc(y) to give you an integer variable.

Something along this line. Good luck!

A simpler version is

splot for [i=1:14] "+" using 1:(y0[i]):(G(x,y0[i]))

but that's not a surface plot.


  Karl

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Thread

Substract value from contour line to surface "laterite@laposte.net" <hematitefr@gmail.com> - 2018-09-17 08:17 -0700
  Re: Substract value from contour line to surface Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2018-09-17 22:25 +0200
    Re: Substract value from contour line to surface "laterite@laposte.net" <hematitefr@gmail.com> - 2018-09-17 22:08 -0700
      Re: Substract value from contour line to surface Karl Ratzsch <mail.kfr@gmx.net> - 2018-09-18 07:46 +0200
        Re: Substract value from contour line to surface "laterite@laposte.net" <hematitefr@gmail.com> - 2018-09-18 00:36 -0700
          Re: Substract value from contour line to surface Gavin Buxton <gavinbuxton@gmail.com> - 2018-09-18 07:34 -0700
          Re: Substract value from contour line to surface Karl Ratzsch <mail.kfr@gmx.net> - 2018-09-18 17:43 +0200
      Re: Substract value from contour line to surface Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2018-09-18 20:11 +0200

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