How to determine where the function is equal to zero
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Lauren Stearns
am 10 Mai 2017
Kommentiert: Lauren Stearns
am 11 Mai 2017
Ultimately I need to figure out the first time my function is equal to zero, but to start I just want to save the x value as a new variable whenever y = 0. Here is my code so far:
close all; clear all; clc
% Prepared by Lauren Stearns
x= 0:10;
x(1)= 1E-5;
f= @(x) (2*besselj(1,x)./x).^2; % The Given Function
y=f(x) % replace the first element in the array
plot(x,y,'b-'); % Plot the Airy pattern
hold on;
xq=0:10; % Points of inquiry
xq(1)=0.0001;
yq3 = interp1(x,y,xq,'cubic'); % Cubic Interpolation
plot(xq,yq3,'b.'); % Plotting the Cubic Interpolation
for y = 0 % Trying to save the x value as a new variable
when y = 0
x = Dark_Fringe
end
xlabel('x');
ylabel('f(x)');
title('Airy Pattern Three');
disp(Dark_Fringe)
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Akzeptierte Antwort
Matt J
am 10 Mai 2017
Bearbeitet: Matt J
am 10 Mai 2017
Ultimately I need to figure out the first time my function is equal to zero,
This is the simpler of the two problems. It is equivalent to finding where the bessel function is equal to zero. Using online tables or your plots, you can see that the first root lies in the interval [3.5,4.5]
>> [xroot,fval] = fzero(@(x) besselj(1,x), [3.5,4.5])
xroot =
3.8317
fval =
7.2971e-17
You can do similarly for the other roots in the interval [0,10]
Weitere Antworten (1)
Ahmed Hossam
am 10 Mai 2017
Try to use symbolic calculation to find 'the zeros'. Otherwise use numerical newton raphson algorithm.
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