Subplot function interfering with appropriate plot display

Question

abbz123 2017-8-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/353788-subplot-function-interfering-with-appropriate-plot-display

回答： Siambou Camara 2019-9-16

When I try to use subplot to show impulse response and unit step response in the same figure, the impulse response plot displays incorrectly. Any idea why subplot is not plotting both the impulse response and unit step response appropriately? Uncomment the second section of code to see the problem. Thanks!

a = [1,-1,0.9]; 
  b = [1];
  n = [-20:120];
  h = impz(b,a,n);
  subplot(1,2,1); stem(n,h);
  title('Impulse response'); xlabel('n'); ylabel('h(n)');
    % %Plot unit step response ex. 2.11 b
    % x = stepseq(0,-20,120);
    % a1 = [1,-1,0.9]; b1 = [1];
    % s = filter(b1,a1,x);
    % n1 = [-20:120];
    % subplot(1,2,2); stem(n1,s);
    % title('Step response'); xlabel('n'); ylabel('s(n)');

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Adam 2017-8-23

编辑：Adam 2017-8-23

I can't run the code as I have no idea what stepseq is. Saying something 'displays incorrectly' is not very useful though. Please explain what is incorrect or attach a picture showing it.

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Answer 1

Star Strider 2017-8-23

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/353788-subplot-function-interfering-with-appropriate-plot-display#answer_278981

在 MATLAB Online 中打开

The impulse and step responses are defined as beginning from 0, and do not exist for negative time. I can’t find ‘stepseq’ in the online documentation.

This works:

a = [1,-1,0.9];
b = [1];
n = [-20:120];
[h,t] = impz(b,a,n);
subplot(1,2,1); stem(t,h);
title('Impulse response'); xlabel('n'); ylabel('h(n)');
%Plot unit step response ex. 2.11 b
% x = stepseq(0,-20,120);
a1 = [1,-1,0.9]; b1 = [1];
s = stepz(b1,a1,120);
n1 = [-20:120];
subplot(1,2,2); stem(n1',[zeros(21,1); s]);
title('Step response'); xlabel('n'); ylabel('s(n)');

I would also stack them vertically rather than plot them horizontally, so use subplot(2,1,1) and subplot(2,1,2) instead.

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abbz123 2017-8-23

Awesome. Thank you so much!

Star Strider 2017-8-23

As always, my pleasure!

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Answer 2

Siambou Camara 2019-9-16

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/353788-subplot-function-interfering-with-appropriate-plot-display#answer_392110

A well-known discontinuous function is impulse function that is defined as: δ(t) = 1 t = 0 0 otherwise. (1) In order to generate impulse function using matlab, follow the same steps as previous section, but this time using the following Matlab code.