I WANT TO KNOW WHY SO MUCH "." (dot) to define a statement, and does it mean something. Swarm.Particles(k).X ???

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RAJESH R
RAJESH R 2020-7-16
评论： Matt J 2020-7-17
for k = 1 : noP
Swarm.Particles(k).X = (ub - lb) .* rand(1,nVar) + lb;
Swarm.Particles(k).V = zeros(1,nVar);
Swarm.Particles(k).PBEST.X = zeros(1, nVar);
Swarm.Particles(k).PBEST.O = inf; % for minimization
end
*** Here they are storing the values in an array; noP = 300; nVar=10*****

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回答（2 个）

Matt J
Matt J 2020-7-16
编辑：Matt J 2020-7-16
It means (probably) that Swarm and some of its fields are struct arrays,
https://www.mathworks.com/help/matlab/matlab_prog/create-a-structure-array.html
It could also be a more general object type,
https://www.mathworks.com/help/matlab/matlab_oop/indexed-reference-and-assignment.html#br09etw-1
It is generally not possible to tell what a variable is just from the way it is indexed. You must use whos() or class() to determine a variable's type.
Image Analyst
Image Analyst 2020-7-16
Swarm is a structure. It has one field called Particles. That field is another structure, but actually not a simple structure, but an array of structures, so it's a structure array with noP structures in the Particles array. Each of those structures in the Particles array has 3 fields: X, V, and PBEST. PBEST is another structure with 2 fields: X and O.
The loop iterates through assigning some value(s) to each structure in the Particles structure array that is a field of Swarm.
Does that help explain it?

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