Integration in gnuplot IS possible!

[3snoW <vas...@gm...>]

Hello,
I'm not sure if this qualifies as "Dev", If it doesn't I'm sorry.
I've searched the web for ways to integrate in gnuplot and only found people
saying it is not possible. Unsatisfied, I decided to see if i could make one
myself. I could :D
This was the result:

intfAux1(a,x,h)=(x>a?(f(x)-f(a))*h+intfAux1(a,x-h,h):0);
intfAux2(a,x,h)=(x<a?(f(x)-f(a))*h+intfAux2(a,x+h,h):0);
intf(a,x)=x>a?intfAux1(a,x-abs(x-a)/90./2,abs(x-a)/90.)+f(a)*(x-a):-intfAux2(a,x+abs(x-a)/90./2,abs(x-a)/90.)+f(a)*(x-a);

Basically, intfAux 1 and 2 are just functions for this thing to work, and
intf(a,b) integrates f(x) from a to b. You can just type this in every time
you want to integrate f(x), or you can download the gnuplot.ini that i made
with this function and put it into your binary folder:
http://old.nabble.com/file/p31856137/gnuplot.ini gnuplot.ini 

Here is also a demonstration of using this:
http://old.nabble.com/file/p31856137/Integrate%2B.png 

There are two problems with this function (that I know of):
-It will most likely not work with self recursive functions because this
function itself is self recursive, and gnuplot has a "stack overflow" limit.
This makes it impossible to double integrate using this function. I made it
so it was not at the limit, it is almost there, so, for example having a
function g(x)=h(intf(0,x)) should not be a problem. By the way, if anyone
knows of a way to set the stack overflow limit higher, I'd appreciate
posting it here.
-The other problem is that it will integrate specifically f(x), so if you
want to integrate another function, g(x) for example, you would have to
create an intg(a,b). To make this task easier, I made it so that if you
replace in those 3 lines of code all the f's with the name of your function,
g for example (again), you would have your intg made. This way you can just
open notepad, use the "replace" command and copy the result to gnuplot.

Let me know if you have any ideas to make it better or if you find any bug
using it! I hope this was helpful!

3snoW
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