Why doesn't heaviside start and end according to the array passed to it?

The stem plot that results from

stem(heaviside(-100:100))

starts at 100 and ends at 200. Why doesnt it start at -100 and end at 100 like the array? Also, why is the amplitude of the stem at 100 only 0.5?

Answer 1

[Walter Roberson]

http://www.mathworks.com/help/matlab/ref/stem.html

If Y is a vector, then the x-axis scale ranges from 1 to length(Y).

What you probably want is:

Y = -100:100;
stem(Y, heaviside(Y));

http://www.mathworks.com/help/symbolic/heaviside.html

heaviside(x) returns the value 0 for x < 0, 1 for x > 0, and 1/2 for x = 0.

The 101'st entry was the one for which the data value was 0.