CODEWITHSUNDEEP
matlabpca
Engine
Engine

Reputation: 5420

plotting eigenvector in Matlab

I'm trying to plot a the eigenvectors of a 2D Dataset, for that I'm trying to use the quiver function in Matlab, here's what I've done so far : 

    % generating  2D data 
clear ;
s  = [2 2] 
set = randn(200,1);
x = normrnd(s(1).*set,1)+3
y = normrnd(s(1).*set,1)+2
x_0 = mean(x)
y_0 = mean (y) 
c = linspace(1,100,length(x)); % color

scatter(x,y,100,c,'filled')
xlabel('1st Feature : x')
ylabel('2nd Feature : y')
title('2D dataset')
grid on
% gettign the covariance matrix 
covariance = cov([x,y])
% getting the eigenvalues and the  eigenwert 
[eigen_vector, eigen_values] = eig(covariance) 
eigen_value_1 = eigen_values(1,1) 
eigen_vector_1 =eigen_vector(:,1)
eigen_value_2 = eigen_values(2,2) 
eigen_vector_2 =eigen_vector(:,2)

% ploting the eigenvectors ! 
hold on 
quiver(x_0, y_0,eigen_vector_2*(eigen_value_2),eigen_vector_1*(eigen_value_1))

My problem is the last line, I get the following error :

    Error using quiver (line 44)
The size of Y must match the size of U or the number of rows of U.

It seems that I'm missing a size here but I can't figure out where! thanks in advance for any hint

Upvotes: 0

Views: 1287

Answers (1)

Tommaso Belluzzo
Tommaso Belluzzo

Reputation: 23675

As the error says, X and Y parameters must have, respectively, the same size of U and V parameters. If you change the last part of your code:

% ploting the eigenvectors ! 
hold on 
quiver(x_0, y_0,eigen_vector_2*(eigen_value_2),eigen_vector_1*(eigen_value_1))

as follows:

x_0 = repmat(x_0,size(eigen_vector_2,1),1);
y_0 = repmat(x_0,size(eigen_vector_1,1),1);

% ploting the eigenvectors ! 
hold on;
quiver(x_0, y_0,eigen_vector_2*(eigen_value_2),eigen_vector_1*(eigen_value_1));
hold off;

your script should properly work.

Upvotes: 1

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