Re: [Gnuplot-info] One more question

[Tatsuro M. <tma...@ya...>]

Hello

This is not direct answer to your reply.

In gnuplot FAQ,

5.4 I need an integration, fft, iir-filter,...! 

Gnuplot has been and is a plotting program, not a data processing or mathematical program suite.
Therefore gnuplot can't do that. Look into the demo file "bivariat.dem" for a basic implementation of
an integration. 

For more sophisticated data-processing read the next section
*******************************************************

Please see demo file "bivariat.dem" how to realize integration by gnuplot script.

Regards

Tatsuro

--- Dieter Jurzitza <die...@t-...> wrote:

> Dear listmembers,
> I recently had the need to integrate a function for some reason. Therefore I 
> wrote a small script that takes the data out of a gnuplot-generated table in 
> a file and calculates the linearly interpolated area between two consecutive 
> x-values of the table I wrote with gnuplot.
> 
> To use this from within gnuplot, I do the following:
> 
> say, the function is x*x and I want to integrate between 0 and 1:
> 
> set xrange[0:1]
> set samples 1000
> set table "dummy.dat"
> plot x*x
> set output
> set terminal X11
> A=system ("integrate dummy.dat")
> print A
> 
> The script "integrate" reads the table and outputs the integral value as 
> described above. The assignment of the output of the system-command 
> A=system(... results in what I want: I have the integral value "at hand" 
> within gnuplot.
> 
> Now I thought about skipping the intermediate step to write to a file:
> 
> set table
> plot x*x
> set output "| integrate -"
> 
> This results in the integral value being printed on the screen. However, I do 
> not know how to "put this output" into a variable like the return value of 
> the system() command can be assigned to.
> 
> Does anybody have an idea whether and how this can be achieved?
> 
> Thank you very much for looking into this,
> take care
> 
> 
> 
> Dieter Jurzitza
> 
> 
> -- 
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