not be plotted (or not correctly be plotted)on general function, need help

[Eric]

Dear matlab/octave expert:



  in 2.1.28(development version),and in matlab 5.3 student



    in simple program



f=0:0.01:3;

y=abs((i*2*pi*f+20*pi)/(i*2*pi*f+2*pi));

plot(f,y)



I get the error response:

error:__plt2vv__: vector lengths must match

error: evaluating if command near line 55, column 3

.......
in matlab, it plot but not what is nog correct, it should not be a constant line, If I tried f=1 and f=10 I get 7.1 and 1.4

need and thanks your help

Eric(address@hidden)