In your above code, you are creating bars of height y (height 1 for first bar, 1 for second bar, 0 for third bar, and so on...) with the bars centered around the values in x (first bar centered at -3, second bar centered at 0, etc).
If you want to have equal spacing between bars, then create an x that has equal spacing between elements.
Otherwise, simply typing
y = [1,1,0,1,3,3,2]
bar(y)
will produce equally spaced bars.
