[metapost] Function defined by a sum
Mojca Miklavec
mojca.miklavec.lists at gmail.com
Fri Nov 2 11:21:19 CET 2007
On 10/31/07, Nicolas FRANCOIS wrote:
> Hi.
>
> I'd like to show the Gibbs phenomenon on an example. For this I'd like to
> draw the partial sums of the Fourier serie :
>
> sum(sin(n*x)/n,n=1..infty)
There is no "sum" (unless you define one), but oyu can use "for" loop:
vardef sin(expr xx) = sind(xx*180/3.14) enddef;
vardef f(expr xx,n) =
save sum;
sum:=0;
for i=1 upto n:
sum := sum+sin(i*(xx))/i;
endfor;
sum
enddef;
beginfig(1);
path p;
p := (0,0)
for j=1 upto 700:
--(j/100,f(j/100,3))
endfor;
draw p scaled 1cm;
endfig;
end.
> For the first five partial sums, I can of course tpe them by hand. But
> what about the sum number 20 ? And 50 ? Is there a "sum" construction
> available in Metapost ? Or some for loop ?
See the metapost manual for using "for" loops.
http://tug.ctan.org/graphics/metapost/mpman.pdf
Mojca
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