Problem with processing function input variable in Matlab

Question

So I am currently working with different datasets. Some are monthly, some daily, but I want quarterly. This is why I wrote the following function:

function y = average2(data, frequency)

% Monthly/Daily data to quarterly data by taking average  
% INPUT     data     Nx2      monthly/daily data
% OUTPUT    y        Mx2      quarterly data
% USAGE     average2(data)

if frequency == 'monthly';
   K = 1:3:(length(data)-3);                      
   quarterly = (data(K, 2)+data(K+1, 2)+data(K+2, 2))/3; 
   timevector = data(K, 1);
   y = [timevector quarterly];

elseif frequency == 'daily';
   y = data*data;                                   %just as an example, not correct calculation

else frequency ~= 'daily' || 'monthly';
   error('Requested frequency not available');

end

(the calculation of daily is not the problem). So my Problem is the following: If I use the monthly option, everything works fine. But everytime I use something different than 'monthly' as frequency in my function, I get the error message:

 Matrix dimensions must agree.

 Error in average2 (line 8)
 if frequency == 'monthly';

Therefore activating the elseif clause and processing the input I get in frequency doesn't work. Does anyone know where I have a mistake? Thanks in advance

Thales · Accepted Answer · 2019-11-21 13:18:26Z

1

To compare strings, use the strcmp (case sensitive) or the strcmpi (case insensitive) functions.

if(strcmp(frequency,'monthly'))
   K = 1:3:(length(data)-3);                      
   quarterly = (data(K, 2)+data(K+1, 2)+data(K+2, 2))/3; 
   timevector = data(K, 1);
   y = [timevector quarterly];

elseif(strcmp(frequency,'monthly'))
   y = data*data;                                   %just as an example, not correct calculation

else % frequency ~= 'daily' || 'monthly' % don't have to do this comparison and is not correctly coded
   error('Requested frequency not available');
end

answered Nov 21, 2019 at 13:18

Thales

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