MATLAB Answers

Spikes in my heaviside function/step functions

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Samantha Zhao
Samantha Zhao on 26 Feb 2019
Commented: Samantha Zhao on 7 Mar 2019
I am trying to plot a simple unit step function (below) using the heaviside function.
x(t) =u(t)−u(t−2)
t = -10:.01:10;
x = heaviside(t) - heaviside(t-2);
plot(x)
The plot results in a unit step function with spikes at 4 and -3.
heavisideSpikes.png
So far my solutions have been editing in the correct values at the appropriate indexes, but it has been getting very tedious. What could be causing this issue? I am also using the 2018b edition and have not noticed this in previous versions.
  2 Comments
Walter Roberson
Walter Roberson on 1 Mar 2019
Also, be careful about what heaviside(0) means. See sympref('HeavisideAtOrigin')

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Answers (1)

Munish Raj
Munish Raj on 1 Mar 2019
Hello Samantha,
The plot in your picture is a mixture of two different plots. It has the intended heaviside as expected.
As you can notice, the y axis of the plot is from [-3 4]. However, the expected heaviside function is plotted in [1 0] on the y axis.
Also please make sure there is no previous plot.
Use the hold off command before plotting the heaviside function.
hold off
to make sure that a new plot is being plotted.
  3 Comments
Samantha Zhao
Samantha Zhao on 7 Mar 2019
I have reinstalled Matlab, opened up a new script, and made sure that there is nothing else being plotted with my heaviside. I'm really at a loss expecially when others are able to produce a normal graph with the exact code!

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