Read EDF files in which channels have different sampling rates

[sam81]

EDF files can have channels with different sampling rates (e.g. https://physionet.org/pn4/sleep-edfx/). It's not clear how the data should be returned in such case. One possibility would be to return each channel as a separate vector (for example in a dictionary). Another approach, which is the one taken by both (FieldTrip)[https://github.com/fieldtrip/fieldtrip/blob/master/edf2fieldtrip.m] and (mne)[https://github.com/mne-tools/mne-python/blob/master/mne/io/edf/edf.py] is to resample the channels to the highest sampling rate used in the EDF file, so that the data can be returned in a matrix. I tried using this approach resampling with the resample function in the DSP module, but was unsuccessful because strangely that function didn't always return the number of samples I expected, e.g.:

using DSP
x = sin(collect(1:10))
y = resample(x, 10.0)

y has 96 elements rather than 100 as I would have expected. For the time being I'm just throwing an error if an EDF file with channels having different sampling rates are detected.