[R] CDF plot

[huang min]

Dear all,

I have define a discrete distribution P(y_i=x_i)=p_i, which I want to
plot a CDF plot. However, I can not find a function in R to draw it
for me after searching R and R-archive. I only find the one for the
sample CDF instead my theoretical one.

I find stepfun can do it for me, however, I want to plot some
different CDF with same support x in one plot. I can not manage how to
do it with stepfun.

Is there any existing function in R to draw the theoretical CDF plot?
Or how to abline other step functions in stepfun? Thanks.