what is the purpose of "simmx.m" M-file in dynamic time warping, in matlab?

[gallabaan]

please explain me what does simmx.m do, comprehensively?

 

[gallabaan]

Re: what is the purpose of "simmx.m" M-file in dynamic time warping, in matlab?

Rob guided me in this regard. i am really thankful to him.
here is the explanation by "Rob".


simmx generates a similarity matrix.

Here's a working implementation:

Dynamic Time Warp in Matlab

The example puts features, as a spectrogram into D1 and into D2 (complex).

The absolute value of D1 and D2 is calculated using abs() which returns a 1xN matrix/vector. These are turned into feature vectors by the lines:

EA = sqrt(sum(A.^2));
EB = sqrt(sum(B.^2));

Where sum(A.^2) produces a sum of the squares of the columns in spectrogram D1, the square root is then taken by sqrt(). This becomes element 1 of EA and so on.

So now the two feature vectors might look something like:

EA = [80.1460385300246 80.4223209993924 81.5990800955345 79.7304932256879 80.4429133365974 81.2984058463773...]
EB = [80.0308851439760 83.5734299550024 84.8833197962066 81.6646072601757 78.5719852908280 77.4648649544494...]

Then the function

M = (A'*B)./(EA'*EB);

Where A' is the transpose of A is multiplied by B. See here for what this is! Matrix multiplication - Wikipedia, the free encyclopedia

This is a way of calculating the cosine distance.

This is divided by

(EA'*EB)

And is plotted as the similarity matrix. The code goes on to compute the best path through the matrix.
thanx Rob