msresample error message: The MZ vector is not evenly nor linearly spaced.

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Aurelie
Aurelie on 3 Aug 2012
I am this error while trying to msresample a Orbi MS spectrum:
Error using msdroppedsamples (line 61) The MZ vector is not evenly nor linearly spaced.
Error in msresample (line 215) [X,Y] = msdroppedsamples(X,Y);
I know that my MZ vector is not linear and has also a lot of O intensities, that is why I want to resample it, but I dont know excatly which parameters I need to adjust, I used this: [MZH,YH] = msresample(MZ, Y, 100000,'RANGE',[150 1200], 'Uniform', false, 'Missing', true, 'showplot', true)
Thanks
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Aurelie
Aurelie on 3 Aug 2012
I put the all code in the post, but for the input I have a CSV file extracted from a HRMS spectrun acquired on a LTQ Orbitrap, the MZ values are definitively not evenly or linearly spaced but I dont understand why this is a problem

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Accepted Answer

Lucio Cetto
Lucio Cetto on 3 Aug 2012
Setting the option MISSING to TRUE should only be used when you are certain that the spacing between MZ values follows a linear or quadratic function of MZ and you are trying to recover some missing points. One example of a dataset like this is the one provided in the example, for instance:
load sample_hi_res
plot(diff(MZ_hi_res),'.')
Here you can se that sometimes 1,2,3,4 or 5 samples are dropped. MSRESAMPLE interpolates these missing points before resampling the data. In most of the instruments, dropped samples come form the background and are removed to reduce the size of the dataset.

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