Create a matrix that changes size according to a variable N

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wissal zaher 2022-7-10

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评论： Steven Lord 2022-7-11

Hello,

I'm working on a project consisting of creating an MPC controller from scratch and the matrices need to be defined in a way where the size can change given a variable N (the prediction Horizon). I've already wirtten the matrices for N=7 but how can I do so for a flexible N input.

The size of the Matrices is given below.

A,B,Q,R, x_min, x_max, u_min, u_max are defined as follow :

A = [1 0.1;0 1]

B = [0.005;0.1]

Q = [1 0;0 1]

R = 0.1

x_min = [-5;-5]

x_max = [5;5]

u_min = -1

u_max = 1

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Answer 1

patrick1704 2022-7-10

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Well, one option on how to e.g. create your

is to do something like this:

Atilde = arrayfun(@(x) A.^x, 0:1:n, 'UniformOutput',false).';

Atilde = vertcat(Atilde{:});

Similarly, you can implement other solutions for your other setups. I would recommend you to just take a look at Matlab-internal functions like: Block diagonal matrix - MATLAB blkdiag - MathWorks Deutschland, Repeat copies of array - MATLAB repmat - MathWorks Deutschland, Apply element-wise operation to two arrays with implicit expansion enabled - MATLAB bsxfun - MathWorks Deutschland, ...

Naturally, doing everything in a for-loop using if-clauses is also an option. It mainly depends on how efficient you need the implementation to be.

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wissal zaher 2022-7-11

编辑：wissal zaher 2022-7-11

For Atilde it worked nicely :)

Bor Btilde I think I have to create a loop .. any ideas ?

And thank you for the reply

Steven Lord 2022-7-11

Bor Btilde I think I have to create a loop .. any ideas ?

Create a for loop?

You may have heard that "for loops in MATLAB are slow." At one time, years ago, that may have been true. It has become less and less true as we've enhanced the language.

If for loops are the right tool for the job, use them.

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