# Need help with integral

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1. Dec 23, 2015

### Lemenks

I carried out a physics experiment and I wanted to analysis the problem with matlab. I have some code in matlab that "works" as in it gives ok result but the numbers used are quite nonsensical, I need help making the reworking the equation with real numbers. I am not sure if this is the correct thread, if not sorry. Here is my code:

Code (Matlab M):

format long;
clear all;

I0=39546.95973;
i=sqrt(-1);
r=0.0;
fid=fopen('plot.txt','w')  %Êý¾ÝÐ´ÔÚplot.txt
for m=1:300
p(m)=m*0.0001-0.015;   %¿ÉÒÔµ÷Õû×÷Í¼²½³¤
In(m)=0;
dddr=0.00001;
for r=0.0:dddr:0.010   %¸ù¾ÝÊÕÁ²ÐÔµ÷Õû»ý·ÖÉÏÏÞºÍ²½³¤
In(m)=In(m)+r*besselj(0,5500000*r*p(m))*exp(-4.325259515570934*10^6*r*r)*exp(-i*(5500000*r*r-27.014528191562999*exp(-4.325259515570934*10^6*r*r)));
end
I(m)=3.025*10^13*dddr^2*I0*(norm(In(m)))^2;
fprintf(fid,'%9.4f  %9.4f  \n',p(m),I(m));
end
fclose(fid)
fclose all;
hold off
plot(p,I);  %»Í¼
hold on
return;

My main problem is using very large numbers like "5500000". What I would like to do, is make the exp(a*exp(b*r^2)) component be the part of the function that determines the number of rings, where a=2Npi and N would determine the number of rings. However I am not sure how to go about normalizing the rest of the constants so that this would be the case.

Mod note: I added code tags. Please do that every time you post code.

2. Dec 23, 2015

### Staff: Mentor

You will have to give more details. What physical problem are you looking at? What is the code actually doing?

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