values on the x-axis are not equally spaced because on every interation you increase L by i, which itself is increased by 1 on every interation:
1st interation: L = 0+0 = 0
2nd L = 0+1 = 1
3rd L = 1+2 = 3
4th L = 3+3 = 6
but you can just use i as your x-parameter for the plot function:
> "is there a way to plot points coming from a for loop as they get out, without using vectors?"
you allready do that using hold on