MATLAB: Help in choosing filter size

cbirgabor

Actually can anyone suggest me how to choose size of the filter in gabor filter ? Can we choose fixed size randomly because many developers has chosen size randomly like 60,30 etc or is their an exact way to find the filter size ? Any help suggestion would be appreciated.

Thanks

Best Answer

Run some images through with different sized filters and see what looks good. Different size filters will detect/enhance different sized objects. The best one is the one that you say is best. It's subjective. When you've picked the right size, I think you'll know it.

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MATLAB: “Invalid second data argument” error while using “plot” function (Lagrange Interpolation)

You are correct, it is complaining because pointy1 is a function handle. You can obtain the output of pointy1 when evaluated at the x values within pointx by calling pointy1(pointx):

clc;
clear all;
pointx = [-2 -1 0 1 2];
pointy1 =@(x) (2 - atan(x));
x = linspace(-5,5);
n = size(pointx, 2);
L = ones(n, size(x,2));
for i=1:n
    for j=1:n
        if (i~=j)
            L(i,:).*(x-pointx(j))/(pointx(i)-pointx(j));
        end
    end
end
y = 0;
for i=1:n
    y = y + pointy1(i)*L(i,:);
end
y1 = y;
plot(pointx, pointy1(pointx), 'r', x, y1, 'c--o');
hold on;

This works because your pointy1 function is vectorized.

MATLAB: FDAtool: Cutoff for “Chebyshev” and “Elliptic”

Hi Alex,

I think there is some misunderstanding regarding the design specification. In IIR filter, if you specify the filter order, the parameters for Butterworth method and the parameters for Chebyshev/Elliptic are different. For Butterworth, like you said, the parameter is the cutoff frequency, i.e. 3dB point. However, for Chebyshev/Elliptic method, you specify the passband and passband ripples. Based on your picture, I assume you are using the default passband ripple (Apass), which is 1dB. This means that between 20 and 150 Hz, the fluctuation cannot exceed 1dB. If you think you can live with a 3dB drop, you can then change your passband ripple (Apass) to 3dB, although such setting is rare in a Chebyshev/Elliptic design.

HTH

Honglei

Best Answer

Related Solutions

MATLAB: “Invalid second data argument” error while using “plot” function (Lagrange Interpolation)

MATLAB: FDAtool: Cutoff for “Chebyshev” and “Elliptic”

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