I use the PSO optimization algorithm and I get the error Unable to perform assignment because the size of the left side is 10-by-1 and the size of the right side is 1-by-3.

This is how I wrote the code I used for the Particle swarm optimization (PSO) function:

function [best_mdl] = myELMtrain_PSO(data, dtrain, Nhid_min, Nhid_max)
actfunc = ["sigmoid", "relu", "leaky_relu", "tanh"];
% Initialize the PSO particles
p = 10;
particles = rand(p, 2);
particles(:, 1) = Nhid_min + (Nhid_max - Nhid_min) * particles(:, 1);
particles(:, 2) = actfunc(randperm(3));
% Evaluate the fitness of each particle
for i = 1:p
    fitness(i) = myELMtrain(data, dtrain, particles(i, 1), particles(i, 2));
end
% Update the particles
for i = 1:p
    for j = 1:p
        if fitness(i) < fitness(j)
            particles(j, :) = particles(i, {});
        end
    end
end
% Find the best particle
best_particle = particles(find(fitness == min(fitness)), :);
% Set the number of neurons and activation function to the best particle
Nhid = best_particle(1);
actfunc = best_particle(2);
best_mdl = myELMtrain(data, dtrain, Nhid, actfunc);
end

When I run the main code and call the function, I get the following error. Please help if possible. Thank you.

Unable to perform assignment because the size of the left side is 10-by-1 and the size of the right side is 1-by-3.

Error in myELMtrain_PSO (line 9)

particles(:, 2) = actfunc(randperm(3));

Error in pso_elm_classifier (line 19)

mdl{i} = myELMtrain_PSO(data, label, 10, 100);

Answer 1

[Torsten]

The reason for the error message is obvious. You can't save a 1x3 array (actfunc(randperm(3))) in a 10x1 array (particles(:, 2)). Further, the array classes differ: while "actfun" is a string array, "particles" is an array of doubles.

[ardalan]

How can I solve this problem? Can you help me?