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how to find sum of square sine wave

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Muhammad Usman Saleem
评论： Image Analyst 2015-5-30
Hi every one; I want to solve that question.Any assistance will be highly appreciable... function called s_wave that computes the sum for each of 1001 values of t uniformly spaced from 0 to 4π inclusive. The input argument is a positive scalar integer n, and the output argument is a row vector of 1001 such sums—one sum for each value of t. You can test your function by calling it with n == 200 or greater and plotting the result, and you will see why the function is called “s_wave”.
Again any assistance will be highly appreciable................
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Muhammad Usman Saleem
Muhammad Usman Saleem 2015-5-29
@thanks Image.. next time i shall take care of it.. Answer my question.. please
Salaheddin Hosseinzadeh
Salaheddin Hosseinzadeh 2015-5-29
Hi Muhammad,
Give it a try it's fairly easy, its a good practice to learn.

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Image Analyst
Image Analyst 2015-5-29
Alright, it looks like you need a lot more help than the hints I gave in my other answer. Here is one way to do it (Put all code in both functions into a single "test.m" and run it):
function test
fontSize = 24;
n = 200;
theSum = s_wave(n);
plot(theSum, 'b-', 'LineWidth', 2);
% Fancy up the plot.
grid on;
caption = sprintf('s_wave : Sum of %d terms', n);
title(caption, 'FontSize', fontSize, 'Interpreter', 'none');
xlabel('t', 'FontSize', fontSize);
ylabel('theSum', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
%============================================================
function theSum = s_wave(n)
t = linspace(0, 4*pi, 1001);
for tIndex = 1 : length(t)
this_t = t(tIndex);
k = 1 : n;
numerator = sin(this_t * (2*k-1));
denominator = 2 * k - 1;
theSum(tIndex) = sum(numerator ./ denominator);
end
%
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Muhammad Usman Saleem
Muhammad Usman Saleem 2015-5-30
Thanks @image... Below is my understanding of my your code which is mark in comments..
function theSum = s_wave(n)
% set input argument n
t = linspace(0, 4*pi, 1001);
%using the linspace function generate a vector from 0 to 1001 with step interval of 4*pi.
for tIndex = 1 : length(t)
% loop over the length of vector t
this_t = t(tIndex);
% i do not get this statement clearly. To me i understand every time the loop run , we call that element of t
k = 1 : n;
numerator = sin(this_t * (2*k-1));
denominator = 2 * k - 1;
theSum(tIndex) = sum(numerator ./ denominator);
end
Image Analyst
Image Analyst 2015-5-30
Yes, every time you run the loop (do one iteration for one value of t), it will do the sum over k for all values of n. The sum over k=1:n is done "vectorized" rather than using a "for" loop, so each variable (numerator, denominator, theSum(t)) is a vector of n elements.

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更多回答（1 个）

Image Analyst
Image Analyst 2015-5-29
k = 1 : n;
numerator = sin(t * (2*k-1));
denominator = 2 * k - 1;
theSum = sum(numerator ./ denominator);
this is just very very basic MATLAB vectorization like you learn within the first hour of taking MATLAB training, so you need to look at this link
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Muhammad Usman Saleem
Muhammad Usman Saleem 2015-5-29
To me i understand the question in the following code..
function [sq] =square_wave(n)
k = 1 : n;
numerator = sin(t * (2*k-1));
denominator = 2 * k - 1;
theSum = sum(numerator ./ denominator);
when i check my code i got an error
Feedback: Your program made an error for argument(s) 1
@image guide me about corrections..thanks in advance
Joseph Cheng
Joseph Cheng 2015-5-29
Kindly put some effort into understanding what Image Analysis has done which gets you 80% of the way there.
Another method is to go
t = 0:.1:4*pi;
k = 1:10;
[T K]= meshgrid(t,k);
Calc= sin((2*K-1).*T)./(2*K-1);

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