matlab and adding step functions

I'm new to Matlab, and I would like to know how to add step functions.
I came up with a function y = u(t)where y(y>=0)=1 and y(y<0)=0.
But how do you add u(1-t)+u(2-t)... etc? Also how do you get the y
axis's sampling rate to get smaller so I have a straight line from the
y value to the x axis.

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