Spikes in my heaviside function/step functions

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.

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.

[Asad Mirza]

Not sure why but when I run the code it comes out without any strange spikes. I am also using MATLAB 2018b.

Just checked it with both MATLAB Online and Octave and I get the same results

[Walter Roberson]

Also, be careful about what heaviside(0) means. See sympref('HeavisideAtOrigin')

Answer 1

[Munish Raj]

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.

[Samantha Zhao]

I have made sure that a new plot is being plotted in matlab. Can you elaborate more on what you mean by my graph being a mixture of two different plots?

[Munish Raj]

The red highlighted plot is the heaviside plot that you are looking for.

The other parts are the extra plots, possibly from another plot function.

[Samantha Zhao]

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!