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POImplementing and ploting a perceptron in MATLAB
 

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    <p>I´m reviewing a code from <a href="http://www.cs.toronto.edu/~hinton/csc321/tutorialcode/perceptron.m" rel="noreferrer">Toronto perceptron MATLAB code</a></p> <p>The code is </p> <pre><code>function [w] = perceptron(X,Y,w_init) w = w_init; for iteration = 1 : 100 %&lt;- in practice, use some stopping criterion! for ii = 1 : size(X,2) %cycle through training set if sign(w'*X(:,ii)) ~= Y(ii) %wrong decision? w = w + X(:,ii) * Y(ii); %then add (or subtract) this point to w end end sum(sign(w'*X)~=Y)/size(X,2) %show misclassification rate end </code></pre> <p>So I was reading how to apply this function to data matrix X, and target Y, but, do not know how to use this function, I understand, it returns a vector of weights, so it can classify.</p> <p>Could you please give an example, and explain it??</p> <p>I´ve tried</p> <pre><code>X=[0 0; 0 1; 1 1] Y=[1 0; 2 1] w=[1 1 1] Result = perceptron( X, Y, w ) ??? Error using ==&gt; mtimes Inner matrix dimensions must agree. Error in ==&gt; perceptron at 15 if sign(w'*X(:,ii)) ~= Y(ii) Result = perceptron( X, Y, w' ) ??? Error using ==&gt; ne Matrix dimensions must agree. Error in ==&gt; perceptron at 19 sum(sign(w'*X)~=Y) / size(X,2); </code></pre> <p>Thanks</p> <p>Thank you for the anwers, I got one more, If I change the Y = [0, 1], what happens to the algorithm?. </p> <p><strong>So, Any input data will not work with Y = [0,1] with this code of the perceptron right?,</strong> </p> <p><strong>-----------------------------EDIT------------------------</strong></p> <p>One more question, if I want to plot the <strong>line that divides the 2 classes</strong>, I know we can get that the line solving linear equation system that has to do with weights, but how, what could I do?, I'm trying something like </p> <pre><code>% the initial weights w_init = [ 1 1 1]'; % the weights returned from perceptron wtag = perceptron(X,Y,w_init,15); % concatenate both Line = [wtag,w_init] % solve the linear system, am I correct doing this? rref(Line') % plot??? </code></pre>
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