# MATLAB: Frequency and Time Relation

frequencyMATLABsignal processingtime seriesvector

Hello,
I am trying to generate a frequency series using the FFT matlab algorithm. It is for a machine tool. Here is my code:
spindle_speed  = 960; % speed is in rpmN = 3;               %Number of teeth in cutter   Fs = 1000;            % Sampling frequency                    T = 1/Fs;             % Sampling period       L = (inv((spindle_speed/60))*1000)*50;             % Length of signal 62.5 for one revolution of tooldelta_T = 62.5*20;t = (0+delta_T:(L-1))*T;        % Time vectorf = Fs*(0:(L/2))/L;             % frequency vector
The problem I am having is that when t starts from 0 then the frequency starts from 0 which is correct, but when t starts from 0+ delta_T, then frequency starts from 0, I dont want it to start from 0. I want the influence of delta_T on the frequency vector.
Does anybody know?