How do i plot the integral against number points used?

4 次查看（过去 30 天）
Michael Lee
Michael Lee 2017-3-15
回答： Rik 2017-3-20
This currently the code i have for prompting the user for input for number of strips. I would like to be able to calculate the integral for n+1=1,2,3,4,5... and plot this against the sample points used. I dont have much of a clue on how to do this, i would suppose to use a for loop and then decrement the no of sample points used for each iteration.
Thanks, very new to matlab.
%Matlab script to evaluate the integral of sin^3(x) between 0 and pi/2
%Prompts the user for input number of strips
prompt = 'Please enter number of strips: ';
n = input(prompt);
%Declaration of constant and vectors
finish = pi/2;
h = finish/n;
points = 0:h:finish; % From 0 to 'finish' with steps of 'h'
esno = 0;
osno = 0;
%Carry out the operator element wise, for each element
v = sin(points).^3;
% Loop for finding sum of even terms
for j = 2:2:n
esno = esno + v(j);
end
% Loop for finding sum of odd terms
for k = 3:2:n-1
osno = osno + v(k);
end
simpval = (h/3)*(v(1) + 4*esno + 2*osno + v(n+1))
%Graphing the convergence of integral with no. of sample points
samplepoints = n+1;
samplepointsvector = 1:1:samplepoints
  4 个评论
显示 2更早的评论
Rik
Rik 2017-3-15
I think I would do something like this:
total_samples=20;
integral_value=zeros(1,total_samples);
for n_samples=1:total_samples
X=linspace(0,pi/2,n_samples+1);
Y=sin(X).^3;
integral_value(n_samples)=trapz(X,Y);
end
plot(1:total_samples,integral_value)
Please let me know if this is what you want, or explain how it doesn't do what you need.

请先登录，再进行评论。

请先登录，再回答此问题。

回答（1 个）

Rik
Rik 2017-3-20
copied from comments
total_samples=20;
integral_value=zeros(1,total_samples);
for n_samples=1:total_samples
X=linspace(0,pi/2,n_samples+1);
Y=sin(X).^3;
integral_value(n_samples)=trapz(X,Y);
end
plot(1:total_samples,integral_value)

类别

在 Help Center 和 File Exchange 中查找有关 Numerical Integration and Differentiation 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by