MATLAB: Sigma of gabor filter

gabor filtersigma values for gabor filter

sigma values in x an y direction should be the same or different in filtering with gabor filter, which one is better and why?what are the factors affecting the decision?

Best Answer

Hi Mahua, you can choose if sigma_x and sigma_y are the same or different values. These values decide about the eliptic shape of the gaussian envelope of the gabor filter. if both sigma are the same, than it's an circle otherwise it would have an eliptic form.

to decide which values to choose depends on your wish for acurate detection. if you use the same value there might be undetected features at specific angles in the frequency space.

for more details watch my file an the related reference: http://www.mathworks.com/matlabcentral/fileexchange/36382-gabor-feature

i would apprechiate your comment/rating.

feel free to ask, if there will be further questions. :)

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MATLAB: Marking a single point on a graph

This first finds the approximate indices for the zero-crossings, then interpolates to find the exact values:

sigma_x = 8;
sigma_y = -12;
tau_xy = -6;
theta = [-90:.05:90];
%Normal Stress
sigma_x1 = ((sigma_x + sigma_y)/2)+(((sigma_x - sigma_y)/2)*(cosd(2*theta)))+(tau_xy*(sind(2*theta)));
sigma_y1 = ((sigma_x + sigma_y)/2)-(((sigma_x - sigma_y)/2)*(cosd(2*theta)))-(tau_xy*(sind(2*theta)));
%Shear Stress
tau_x1y1 = -(((sigma_x - sigma_y)/2)*(sind(2*theta)))+(tau_xy*(cosd(2*theta)));
zci = @(v) find(v(:).*circshift(v(:), [-1 0]) <= 0);                    % Returns Approximate Zero-Crossing Indices Of Argument Vector
tauzix = zci(tau_x1y1);                                                 % Approximate Zero-Crossing Indices
for k = 1:numel(tauzix)
    xval(k) = interp1(tau_x1y1(tauzix(k)-1:tauzix(k)+1), theta(tauzix(k)-1:tauzix(k)+1), 0);    % ‘Theta’ Values At Zero-Crossings
end
%plot
plot(theta, tau_x1y1)
hold on
plot(xval, zeros(size(xval)), 'pg')
hold off
xlabel('Degree of Rotation'), ylabel('Shear Stress'),title('Shear Stress Based on Rotation')
grid on, axis equal

MATLAB: Hey there, I am trying to write a code for 2D-Mohr’s circle and i need to generate a circle for x value of Sx, radius(r) of T.

syms Th;
km = (2*T)/(Sx-Sy);
eq1 = tan(2*Th) == km;
solvth = solve(eq1);
solvth = double(solvth)

Hope this will work

Best Answer

Related Solutions

MATLAB: Marking a single point on a graph

MATLAB: Hey there, I am trying to write a code for 2D-Mohr’s circle and i need to generate a circle for x value of Sx, radius(r) of T.

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