*** Write a function called triangle_wave that computes the sum (−1) sin(2 +1) (2 +1) 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 v
3 次查看(过去 30 天)
显示 更早的评论
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/164258/image.png)
this is my code and I need your help I couldn't figure out where I'm making mistake.
function theSum = triangle_wave(n)
t = linspace(0, 4*pi, 1001);
for tIndex = 1 : length(t)
this_t = t(tIndex);
k = 1 : n;
numerator = ((-1)^k).*sin(this_t * (2*k+1));
denominator = (2 * k + 1)^2;
theSum(tIndex) = sum(numerator ./ denominator);
end
5 个评论
Jan
2017-5-21
@Waseem Iqbal: It is okay. This happens frequently and we all remind newcomers to improve the format. Now let's come back to the question for clarification:
You forgot to mention, why you assume that there is a mistake. Please explain this.
采纳的回答
Jan
2017-5-21
编辑:Jan
2017-5-21
denominator = (2 * k + 1) .^ 2;
Use the elemtnwise .^ instead of the matrix operation ^ . The same for "(-1)^k" .
The corresponding error message is clear:
Error using ^
Inputs must be a scalar and a square matrix.
To compute elementwise POWER, use POWER (.^) instead.
[EDITED] The formula contains: "Sum from k=0 to n", you code contains:
k = 1:n;
Replace this by k = 0:n. It will be more efficient to move the definition before the loop and pre-allocate the output:
function S = triangle_wave(n)
t = linspace(0, 4*pi, 1001);
S = zeros(size(t)); % Pre-allocation
k = 0:n; % Not 1:n
for tIndex = 1 : length(t)
numerator = ((-1) .^ k) .* sin(t(tIndex) .* (2 * k + 1));
denominator = (2 .* k + 1) .^ 2;
S(tIndex) = sum(numerator ./ denominator);
end
6 个评论
Jan
2017-5-21
@Waseem: Look at the formula: Look at the limits of the sum, it goes from k = 0 to n. Do you see it under and above the Sigma? With the zeros() command I've pre-allocated the output. Search in this forum for "pre-allocation".
rishabh gupta
2018-2-10
can you please tell how is the value of k changing when it is placed outside the loop??
更多回答(2 个)
Vikrant dhall
2018-4-29
function v = triangle_wave(n) t = linspace(0,4 * pi, 1001); v = zeros(size(t)); p = 1; for tt = 0:length(t) suma = 0; for k = 0:n suma = suma + (((-1 .^ k) .* sin((2.*k+1).*tt)) / ((2.* k+1).^2)); %suma end %suma v(1,p) = suma; p = p + 1; end end
What is the error in this can anyone please help
1 个评论
Vikrant dhall
2018-4-29
function v = triangle_wave(n)
if true
% code
end
t = linspace(0,4 * pi, 1001);
v = zeros(size(t));
p = 1;
for tt = 0:length(t)
suma = 0;
for k = 0:n
x = ((-1 .^ k) .* sin((2.*k+1).*tt)) / ((2.* k+1).^2);
suma = suma + x;
%suma
end
%suma
v(1,p) = suma;
p = p + 1;
end
end
另请参阅
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!