# Generating Exaustive Parameter Combinations

2 views (last 30 days)
Florian Rössing on 29 Nov 2022
Commented: Bruno Luong on 3 Dec 2022
Hi Everyone.
I want to create many Simulink.SimulationInput Objekts to simulate with many parameters.
To achieve this I am looking for a way to create exhaustive combinations of parameters.
I have not yet decided but thought, that structs might be usefull here. So far the Idea looks like this:
%function simIn = createSimIn(ModelName,Parameters)
% ParameterNames = fieldnames(Parameters);
% for i = 1:length(Parameters)
% for ii = 1:length(ParameterNames)
% simIn(i) = simIn(i).setVariable(ParameterNames(ii),Paramters(i).(ParameterNames(ii)),'Workspace',simIn(i).ModelName);
% end
% end
%end
To get this running I would need a way to create a struct with and exhaustive combination of the parameters.
Lets say I have parameters:
a = 1:5;
b= 0:0.1:0.4;
Example = struct('a',num2cell(a),'b',num2cell(b))
Example = 1×5 struct array with fields:
a b
I would want to create a struct that contains an exhaustive combinations, for a known number of parameters and equal lengths i can do:
Example = struct('a',num2cell(sort(repmat(a,1,length(b)))), ...
'b',num2cell(repmat(b,1,length(a),1)))
Example = 1×25 struct array with fields:
a b
But I would want to do it for an arbitrary number of parameters and arbitrary multiplicities for the parameters. Is there an easier way to do this?
Jan on 29 Nov 2022
What about using meshgrid or loops?
Florian Rössing on 30 Nov 2022
Loops are my fallback option, but they are ugly, so i hoped there might be a nicer way to doing this.
Meshgrids i never heard of before, but I just looked it up, looks like you can only use that for 2 and 3D Data.

Bruno Luong on 30 Nov 2022
Edited: Bruno Luong on 30 Nov 2022
I start with a scalar structure s rather than the structure array, since paramereters might have different lengths
s=struct('a', 1:3, ...
'b', 1:4, ...
'c', 1:5)
s = struct with fields:
a: [1 2 3] b: [1 2 3 4] c: [1 2 3 4 5]
c = struct2cell(s);
n = length(c);
[c{:}] = ndgrid(c{:});
A = reshape(cat(n+1,c{:}),[],n);
sarg = [fieldnames(s)'; num2cell(num2cell(A),1)];
Sexpand = struct(sarg{:})'
Sexpand = 1×60 struct array with fields:
a b c
Bruno Luong on 2 Dec 2022
Sorry my code is never intended to work on anything different than numerical data.
Bruno Luong on 3 Dec 2022
Here is the fix:
s=struct('a', 1:3, ...
'b', 1:4, ...
'c', 1:5, ...
'str', "Test")
s = struct with fields:
a: [1 2 3] b: [1 2 3 4] c: [1 2 3 4 5] str: "Test"
c = cellfun(@num2cell,struct2cell(s),'unif',0);
n = length(c);
[c{:}] = ndgrid(c{:});
A = reshape(cat(n+1,c{:}),[],n);
sarg = [fieldnames(s)'; num2cell(A,1)];
Sexpand = struct(sarg{:});
Sexpand(1)
ans = struct with fields:
a: 1 b: 1 c: 1 str: "Test"
Sexpand(end)
ans = struct with fields:
a: 3 b: 4 c: 5 str: "Test"

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