I can't see the cosine graph. How do I generate the cosine graph using 2^10 samples?

Question

Byungho 2024-4-4，20:05

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2103086-i-can-t-see-the-cosine-graph-how-do-i-generate-the-cosine-graph-using-2-10-samples

回答： Voss 2024-4-4，20:24

采纳的回答： Voss

在 MATLAB Online 中打开

deltat=0.1;

nsamples=2^10;

time=[0 : deltat : deltat*(nsamples-1)];

for i=1: nsamples

ydata(i,:)=[5+10*cos(2*pi*time+pi/6)];

end

figure(1);

plot(time,ydata,'b')

I try to generate the cosine graph with 2^10 samples.

I used 1024 (=2^10) time samples to create the cosine graph.

The time interval is 0.1 seconds.

Could you explain why I have 1024*1024 ydata rather than 1*1024 ydata?

How do I create a cosine graph using time sample data?

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Answer 1

Voss 2024-4-4，20:24

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2103086-i-can-t-see-the-cosine-graph-how-do-i-generate-the-cosine-graph-using-2-10-samples#answer_1436736

在 MATLAB Online 中打开

for i=1: nsamples

ydata(i,:)=[5+10*cos(2*pi*time+pi/6)];

end

That calculates 5+10*cos(2*pi*time+pi/6) and assigns it to the first row of ydata, then calculates the same thing again and assigns it to the second row of ydata, etc., etc., for nsamples rows. At the end ydata is a matrix where each row is the same and each row contains the calculated signal for all times.

What you mean to do is simpler than that; just calculate ydata once:

deltat = 0.1;

nsamples = 2^10;

time = (0 : nsamples-1) * deltat;

ydata = 5+10*cos(2*pi*time+pi/6);

figure(1);

plot(time,ydata,'b')

% zooming in

figure

plot(time,ydata,'b')

xlim([0 10])