Why these two codes produce different graphs? How can I make the second graph be like the first?

Question

sadel 2011-6-17

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1st:

    t=0:0.3:10;
step(c2d(tf(1,[1 1]),0.3),t);

2nd:

t=0:0.3:10;
[y,t]=step(c2d(tf(1,[1 1]),0.3),t);
plot(t,y)

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sadel 2011-6-17

Any idea?

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Answer 1

Arnaud Miege 2011-6-17

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Fangjun's correct. To get the same plot, use stairs:

stairs(t,y)

HTH,

Arnaud

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Answer 2

Fangjun Jiang 2011-6-17

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The results are same if you see it like this.

figure;
plot(t,y,'+');

I think the reason is: you are calculating the step response of a discrete system so the plot shown in your first step() line shows the results as the value at every discrete time step. The plot shown in your plot() line is interpreted by the plot() command.