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I have some signal data from my lab that I want to present but I want to be able to say whether the signals I have are significantly different or not. I thought I could use cross-correlation. I haven't seen cross-correlation, convolution, or DFFT, etc. since the university course I took on signal processing. I still have the Python and Matlab programs that will perform a cross correlation on .txt files. What I want to know is what should I be looking for if the signals are 'pretty close' or not significantly different under a Normal distribution - a peak at the centre? The thing is my data now doesn't depend on time - it is UV-vis absorption spectra of chemicals that I want to compare based on their wavelength. Is the y-axis the correlation coefficient between 0 and 1? And is it OK to replace the time-lag in seconds with say, wavelength?

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Difficult to say unless you specify what your software calculates and how the ccf is normalised. Usually you would design it so a perfect match gave a ccf of unity at zero lag.

In general you expect to get a big peak in the centre with a FWHM that is roughly the sum of the spectral resolutions of your individual spectra.

Using wavelength on the x-axis is quite standard - e.g. Cross correlation as a means of measuring the redshift of galaxies, using a similar galaxy spectrum at rest as a template.

The x-axis of your CCF in such cases is a wavelength difference.

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