extract multiple submatrices from a large matrix based on specific criterion

I have a Matrix A (162301x13 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

Answer 1

[madhan ravi]

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

[madhan ravi]

????? What ?

[Priscilla Schmitz]

Sorry, your answer helped me! thanks a lot

[Priscilla Schmitz]

Since it would be too time consuming if i change the ID number manually, do you know an alternative way to do it? like a loop or something?

Those are the IDs that I have (attached)

[madhan ravi]

u = unique(T.id);
for k = 1:u
    Wanted{k} = T{T.id==23,:};
end

[Priscilla Schmitz]

When i use this code, matlab stores only T.id==23 k times and that is not what i need. i need to have k number of submatrices for each ID number at the end

[madhan ravi]

u = unique(T.id);
for k = 1:numel(u)
    Wanted{k} = T{T.id==u(k),:};
end

[Priscilla Schmitz]

Now it works!

Thank you a lot

[Priscilla Schmitz]

Just one last question, how do I conver this multiple cell arrays (1x379) in multiple matrices?

[madhan ravi]

cat(3,Wanted{:}) % works only if each cell has same number of rows otherwise keeping it this way is the only option.