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POHow do I ask MATLAB to run my function for each column in a matrix?
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copied!<p>I'm nearly finished with my RA job for my professor; however, I have a programming question that is stumping me. The last step in the implementation that my professor asked me to do is that I need to run all the functions that I wrote for a matrix. What is going to happen is that for each column of that matrix, I will call a function that I wrote, which for example, looks like this:</p> <pre><code>function [xpeaks, xtroughs]=peaktrough(x,cutoff) % This function is a modified version of the algorithm used to identify % peaks and troughs in a series of prices. This will be used to identify % the head and shoulders algorithm. The function gives you two vectors: % PEAKS - an indicator vector that identifies the peaks in the function, % and TROUGHS - an indicator vector that identifies the troughs of the % function, and a MATRIX - ptdata, which is a matrix of the location and % the value of the peak/trough. % The input is the vector of exchange rate series, and the cutoff % used for the selection of the final peaks and troughs. % Finding all possible peaks and troughs of our vector. [posspeak,possploc]=findpeaks(x); [posstrough,posstloc]=findpeaks(-x); posspeak=posspeak'; posstrough=posstrough'; % Initialize vector of peaks and troughs. numobs=length(x); prelimpeaks=zeros(numobs,1); prelimtroughs=zeros(numobs,1); numpeaks=numel(possploc); numtroughs=numel(posstloc); % Indicator for possible peaks and troughs. for i=1:numobs for j=1:numpeaks if i==possploc(j); prelimpeaks(i)=1; end end end for i=1:numobs for j=1:numtroughs if i==posstloc(j); prelimtroughs(i)=1; end end end % Vector that gives location. location=1:1:numobs; location=location'; % From the list of possible peaks and troughs, find the peaks and troughs % that fit Chang and Osler [1999] definition. % "A peak is a local minimum at least x percent higher than the preceding % trough, and a trough is a local minimum at least x percent lower than the % preceding peak." [Chang and Osler, p.640] peakcutoff=1.0+cutoff; % cutoff for peaks troughcutoff=1.0-cutoff; % cutoff for troughs % First peak and first trough are initialized as previous peaks/troughs. prevpeakloc=possploc(1); prevtroughloc=posstloc(1); % Initialize vectors of final peaks and troughs. vectpeak=zeros(numobs,1); vecttrough=zeros(numobs,1); % We first check whether we start looking for peaks and troughs. for i=1:numobs if prelimpeaks(i)==1; if i>prevtroughloc; ratio=x(i)/x(prevtroughloc); if ratio>peakcutoff; vectpeak(i)=1; prevpeakloc=location(i); else vectpeak(i)=0; end end elseif prelimtroughs(i)==1; if i>prevpeakloc; ratio=x(i)/x(prevpeakloc); if ratio<troughcutoff; vecttrough(i)=1; prevtroughloc=location(i); else vecttrough(i)=0; end end else vectpeak(i)=0; vecttrough(i)=0; end end % Now from the final peaks and troughs, we now write the matrix of the % peaks and troughs of the exchange rate series. xpeaks=find(vectpeak); xtroughs=find(vecttrough); end </code></pre> <p>Now, the thing is, however, for different columns, I will end up with vectors of different sizes. What I want to know is, how do I go about it? I have 20 user-created functions, and for each function, I need to run each of the columns in the 5000 x 10000 matrix.</p> <p>A friend of mine suggested that I write a function that gets the nth column of my matrix, and then returns it as a vector, then run each of the functions of my matrix for that resulting vector. Any other ideas? Actually, to be honest, I do not know how to write that function that he suggested. Thanks!</p>

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