Karl - are you reading the correct columns? For example, on my Mac, the time array
time = xlsread('Lab-2ciii.xlsx','A1:A300');
is empty, and the signal array
signal = xlsread('Lab-2ciii.xlsx','B1:B300');
has just a handful of elements
Both correspond to the first and second columns of your spreadsheet. I suspect you want columns E (which seems to correspond to time) and either H, K, or N...all of which have 300 elements.