It is unclear what you want:
maybe you forgot to underline your variable name
function_data = angleAnalysis_withPlots('C:/research bme/excel files/Participant 009-002.xlsx')
or you wanted to define a function, then better use:
result = angleAnalysis_withPlots('C:/research bme/excel files/Participant 009-002.xlsx')
function data = angleAnalysis_withPlots(myInput)
% your code here
% some stuff like making numbers from chars
data = double(myInput);
end
