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Discrete Fréchet distance

Compute the discrete Fréchet distance [1] between two curves specified by ordered discrete points in n-dimensional space according to algorithm in [2].

The implementation is based on MATLAB function by Zachary Danziger [3]; however, it does not provide computation of coupling sequence. Depending on the number of points and the number of dimensions, this MEX function is 10 to 50 times as fast as [3].

Currently, only the Euclidean (l^2), taxicab (l^1) and the maximum (l^\infty) norms can be used as distance functions (specify 2, 1 or -1 respectively as the third argument). If you want to use a custom distance function, please implement it in directly in the C code.

Installation

Open the repo directory in MATLAB and type

mex DiscreteFrechetDistance.c

If you want to add the directory to your path, type

addpath(cd)
savepath

Usage example

Calling syntax: d = DiscreteFrechetDistance(c1, c2, normID), where c1 and c2 are matrices with curve points and the optional argument normID specifies the desired norm (distance function).

:warning: In contrast to [3], this function requires that input matrices contain point coordinates in columns, i.e. the matrix shape should be <number of dimensions> x <number of points in curve {1, 2}>.

x1 = linspace(-2, 2, 200);
y1 = x1.^2 + 0.2.*x1 + 2;

t2 = linspace(0, 4, 300);
x2 = 8.*sin(0.1.*t2) - 1;
y2 = 2.*cos(0.9.*t2 + 0.2) + 6;

t3 = linspace(0, 1, 1000);
x3 = 2.*sin(10.*t3);
y3 = 10.*cos(2.*t3 + 0.2) + 3;

figure
plot(x1, y1);
hold on
plot(x2, y2);
plot(x3, y3);
hold off
legend('C1', 'C2', 'C3')

% Notice the matrix layout
d12 = DiscreteFrechetDistance([x1; y1], [x2; y2]);
d23 = DiscreteFrechetDistance([x3; y3], [x2; y2]);
d13 = DiscreteFrechetDistance([x3; y3], [x1; y1]);

fprintf('DFD(C1, C2) = %5.2f\n', d12);
fprintf('DFD(C2, C3) = %5.2f\n', d23);
fprintf('DFD(C3, C1) = %5.2f\n', d13);

Known issues

References:

[1] Wikipedia: Fréchet distance

[2] Eiter, T. and Mannila, H.: Computing Discrete Fréchet Distance. Technical Report 94/64, TU Wien, 1994; available [online].

[3] Danziger, Z.: Discrete Fréchet Distance. Available [online].