# MATLAB: Signal Processing – Cross-Correlation to obtain Lag times.

xcorr

I have written code that produces a graph giving the xcorr coeff of two stochastic electromyogram signals: sEMGL and sEMGbR. % x=(sEMGL); y=(sEMGbR); [c,lags]=xcorr(x,y,'coeff'); figure (8); plot (c,lags) % My question is how to write code in Editor so that in the command window I can type 'time lag =' to obtain this scalar value in milliseconds. A secondary question is to find the derivative of each signal in order to calculate the rate of change in each signal: to evaluate whether the time lag between the signals varies in relation to the rate of change in each signal.
Please help. Kind regards, Trudy

#### Best Answer

• Hi, you need to know the sampling interval of course. Here I assume the sampling interval is 1 msec and delay one signal ten samples, 0.01 seconds.
dt = 1e-3;x = randn(100,1);y =[zeros(10,1); x(1:end-10)];[c,lags] = xcorr(y,x,40,'coeff');[~,index] = max(abs(c));fprintf('Time lag = %2.3f seconds\n',lags(index)*dt)