[scilab-Users] Reg :: Area Between two curves

[Sumit Adhikari]

Dear Antoine and Samuel,

Thanks for the replies. I am using Antoine's function. It is working great!.
Thanks  Antoine, for everything :)
Regards,
Sumit

On Wed, Oct 5, 2011 at 8:54 AM, Antoine Monmayrant <
antoine.monmayrant at laas.fr> wrote:

> Le 04/10/2011 22:41, Samuel Gougeon a écrit :
>
>  Le 04/10/2011 15:47, Sumit Adhikari a écrit :
>>
>>> Hello All,
>>>
>>> If I have two curves then how do I shade the area between two curves in
>>> scilab.
>>>
>>> I am plotting data files and using scilab plot function.
>>>
>> There are at least 4 ways for doing that. The best one depends on if your
>> curves
>> share the same x or not, and/or if they are crossing each others or not...
>>
>> After a plot, you may use  e = gce(); e=e.children(1);  and then
>> either e.polyline_style=5;  e.foreground=<index of the color you want>
>> or e.fill_mode="on"; e.background=<index of the color you want>
>> xfpoly(...) could also be used.
>> Anyway, you will likely have to complete your data by adding a heading
>> and a trailing well-chosen point to each curve.
>>
>> Have a try and optimize according to your data.
>>
>> The area between both curves may also be considered as a polygone to be
>> filled.
>>
>> HTH
>> Samuel
>>
>
> For two curves y1 and y2 that share the same x axis, I have made this quick
> and dirty function:
>
> BetweenCurves(x,y1,y2);
>
> Here is an example:
>
> x=[-10:10];y1=x+10;y2=x.*x;
> BetweenCurves(x,y1,y2);
>
>
> Here is the source code below:
>
>
> //////////////////////////////**//////////////////////////////**
> //////////////////////////////**//////////////////////////////**//////
> // Plot area between two curves
> function [h,epoly,ey1,ey2]=**BetweenCurves(x,y1,y2,**varargin)
> //
> //      Plots two curves and fill the area in between
> //
> //      INPUTS:
> //              x       vector (1,n) of horizontal coordinates
> //              y1      vector (1,n) value of 1st curve y1(x)
> //              y2      vector (1,n) value of 2nd curve y2(x)
> //       -- optional inputs: pairs "keyword","value" --
> //              "handle",h      handle to the graphic window to use
> //              "axis",a      handle to the graphic axis to use
> //              "foreground", colorid   id of the color to use for painting
> the area
> //              "background", colorid   id of the color to use for curves
> stroke
> //
> //      OUTPUTS:
> //              h       handle to the graphic window used
> //              epoly   handle to the polygone that fill the area in
> between
> //              ey1     handle to first curve
> //              ey2     handle to second curve
>
> //default values for optional argument
>      hfig=-1;
>      background=%nan;
>      foreground=%nan;
> // scan varargin for optional parameter pairs (they can appear in any
> order)
>   for i=1:2:length(varargin)
>      keyword=varargin(i);
>      value=varargin(i+1);
>      select keyword
>         case "handle" then
>            hfig=value;
>            scf(hfig);
>         case "axis" then
>            axis=value;
>            sca(axis);
>            hfig=axis.parent;
>         case "background" then
>            background=value;
>         case "foreground" then
>            background=value;
>      end
>   end
> // special treatment for handle (aka hack alert)
>   if typeof(hfig) ~= "handle" then
>      hfig=scf();
>   end
>   h=hfig;
>   scf(hfig);
>   xfpoly([x,x($:-1:1)],[y1,y2($:**-1:1)]);
>   epoly=gce();
>   plot(x,y1);
>   ey1=gce();
>   plot(x,y2);
>   ey2=gce();
> // background setting
>   if (~isnan(background)) then
>      // optional background specified
>      epoly.background=background;
>   else
>      // default background
>      epoly.background=color("**gray87");
>   end
> // foreground setting (as for background)
>   if (~isnan(foreground)) then
>      epoly.foreground=foreground;
>      ey1.children.foreground=**foreground;
>      ey2.children.foreground=**foreground;
>   else
>      epoly.foreground=color("**gray65");
>      ey1.children.foreground=color(**"gray65");
>      ey2.children.foreground=color(**"gray65");
>   end
> endfunction
> //////////////////////////////**//////////////////////////////**
> //////////////////////////////**//////////////////////////////**//////
>
> It's far from perfect but it does what I need.
> Hope it helps,
>
> Antoine
>



-- 
Sumit Adhikari,
Institute of Computer Technology,
Faculty of Electrical Engineering,
Vienna University of Technology,
Gußhausstraße 27-29,1040 Vienna
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