Write a function called triangle_wave

The function computes the sum Σ((−1^k)*sin((2k+1)(t))/((2k+1)^2)) for each of 1001 values of t uniformly spaced from 0 to 4π inclusive. The input argument is a scalar non-negative 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 == 20 or greater and plotting the result and you will see why the function is called “triangle_wave”.

For this question, I have written a function to solve it but my code is always rejected by the grader.

This is the plot I get whenever I plot my function;

My attempt made use of a nested for loop as shown:

Please any clue to get my code right will be highly appreciated. Thanks

[Jan]

Please post your code as text using the "{} Code" format button. Using a screenshot is less convenient, when parts of the code could be used by copy&paste. Now posting an answer requires to retype your code, which is very tedious, because TMW decided to insert a bunch of GUI elements between the question and the answer, such that scrolling is obligatory, if you do not have a 56'' monitor with Giga pixels.

[Stephen23]

@Okongwu Chukwuebuka: please edit your question and delete the useless screenshot and replace it with actual text that we can run. Make sure to format your code by selecting it and then clicking the {} Code button.

Answer 1

[Jan]

Do you have any useful details about the "rejection of the grader"? Is this a Cody Coursework? I start to detest this, because many students struggle with the automatic rejection without useful information. I do not believe in automatic teaching.

Perhaps it matters than 4*pi is not 12.5664. Try:

m = linspace(0, 4*pi, 1001)

You have to reset sump to 0 for each time point. Move the sump = 0 inside the for t loop.

By the way: The iterative growing of arrays is a bad programming practice. Care for a proper pre-allocation is real programs:

a = zeros(1, length(m));
...
for t = 1:length(m)
  ...
  sump = 0;
  for k = 0:n
     ...
  end
  a(t) = sump;
end

[Okongwu Chukwuebuka]

Thanks a million! You have helped to reignite my zeal for coding once more.

[Okongwu Chukwuebuka]

Answer 2

[Torsten]

Use (-1)^k instead of (-1^k).

Best wishes

Torsten.

[Jan]

+1, Most likely. The text of the question contains (-1^k) already, which is equivocal.

[Okongwu Chukwuebuka]

Thank you too, Your contribution was helpful.

Answer 3

[Konstantinos Pantazis]

I am new to Matlab but it seems that how I proceed below gives the correct answer.

 function v=triangle_wave(n)
t= *linspace*(0,4*pi,1001);
k=0;
l=0;
for k=0:n
    l=l+((-1)^k)*sin((2*k+1).*t)./(2*k+1)^2;
end
v=l;

Answer 4

[Theocharis Maitis]

function [v]=triangle_wave(n)

t=linspace(0,4*pi,1001);

v=0;

for k=0:n

v=v+((-1)^k)*sin((2*k+1).*t)./(2*k+1)^2;

end

plot(v)