MATLAB: Extract multiple submatrices from a large matrix based on specific criterion

submatrix

I have a Matrix A (162301×13 double) which first column contains 625 different ID numbers (they repeat that is why i have 162301 rows) and the other columns contain SL values for 12 different frequency values.

i need to extract submatrices from this large matrix for each unique ID value. For example (see attached), ID 23 contains 8 rows of values for the SLs columns and i want to extract this submatrix from the large matrix.

Any ideas?

Thanks

Best Answer

T=readtable('mydatfile.csv')% Note here it’s just your filename;
Wanted = T(T.id==23,:) %

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Try this:

Mcat = [M1 M2];

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It woiuld be necessary to convert column B to strings in order for datetime to parse it, however that is not difficult. Grouping them is strraightforward, using either findgroups or the third output of unique. The accumarray function might be the best way to segregate them.

Example —

a = rand(10, 5);                                            % Create Matrix

A = [[3 3 3 4 4 6 6 6 6 7]' a];                             % Create Matrix
G = findgroups(A(:,1));
M = accumarray(G, (1:size(A,1)).', [], @(x){A(x,:)});
Cell_1 = [M{1}]
Cell_3 = [M{3}]

This does not include the datetime calls, howefver that would be straightforward if the date and time numbers needed to be converted.

Best Answer

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