MATLAB: Subtracting elements with constraints

array

Hi all,

I have an array A and I need to subtract the elements of each column using the cumsum function:

B=bsxfun(@minus, A(1,:), cumsum(A(2:end,:)));

However I have some constraints that should not violated (min=1.3, max=11.7) Is there any way to do the calculations within these limits?

thanks

Best Answer

Your question is not clear where you want these constraints applied.

Option one: constrain output values:

 B = bsxfun(@minus, A(1,:), cumsum(A(2:end,:)));
 B = max(1.3, min(11.7, B));

Options two: constrain cumsum values:

 tmp = max(1.3, min(11.7, cumsum(A(2:end,:))));
 B = bsxfun(@minus, A(1,:), tmp);

Related Solutions

MATLAB: Help with an optimization problem

Put all your vectors together, each as a column, but multiply by -1.

A = -1[a(:), b(:), c(:), ...];

and a goal vector the same length and negative

b = -60 * ones(length(a),1);

Now use a binary optimizer on 20 variables, in which the objective function is the sum of the decision variables (which gets you the smallest number of items selected), and using A and b as the linear inequality constraints, which are constraints of the form A*x <= b

With only 20 variables you can evaluate

X = (dec2bin(0:2^20-1, 20) - '0').';
min_test = A*X <= b;
meets_min = all(min_test, 1);
candidates = X(:,meets_min);
numvecs_for_candidates = sum(candidates,1);
best_candidates_idx = find(numvecs_for_candidates == min(numvecs_for_candidates));
best_candidates = candidates(:,best_candidates_idx);

best_candidates will then be an array that includes all of the cases where, with the minimum number of vectors, the sums were all at least 60.

To modify this so that only 3 sums need to be above 60,

meets_min = sum(min_test, 1) >= 3;

And no optimization routine needs to be run, every combination is tested.

This should be pretty feasible for 20 variables. Probably it would be feasible for 24 as well. By 30 or so you would be pushing things and might run out of memory.

I constructed this particular way with the negatives because this A and b matrix constructed are exactly what you would need to pass as A and b matrices to the various minimizers such as fmincon() or ga() or one of the integer programming routines. (You would not actually use fmincon() for this because fmincon() is not suitable for binary decision variables.)

MATLAB: Subtracting elements in an array

If I understand correctly what you are asking, this will work:

A=[10 9 10; 1 2 3; 4 5 6]
B = cumsum(-A(2:end,:))+A(1,:)
A =
    10     9    10
     1     2     3
     4     5     6
B =
     9     7     7
     5     2     1

Best Answer

Related Solutions

MATLAB: Help with an optimization problem

MATLAB: Subtracting elements in an array

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