How to use 'find' function in matlab

In the below code, We have a random population with structures Position (3D array) and Cost. I need to check whether a particular element present in the population If it does then I want to remove it from the population. I'm using 'find' function for doing it. It was working fine with arrays but with structures I'm getting error below error

_ Undefined operator '~=' for input arguments of type 'struct'_

Here is the code

clc; clear all;
varMin   = -5;           
varMax   =  5; 
D        =  3;
VarSize  = [1 D]; % Decision Variables Matrix Size
NP      = 3;

empty_individual.Position   = [];
empty_individual.Cost       = [];

P  = repmat(empty_individual, NP, 1);

addpath('E:\Dimensionality Reduction\DR & Optimization\Data\Objective Functions');
CostFunction = @(x) sphere(x);

%%Generating random population

for i = 1:NP
    P(i).Position = unifrnd(varMin, varMax, VarSize);
    P(i).Cost     = CostFunction(P(i).Position);
end

xi = [1 1 1];                % xig

P  = P(find(P ~= xi));

[KSSV]

You cannot use find like that. _P is 3x1 structure, what you want to find exactly?

[Atinesh Singh]

Can you suggest any alternative for it.

[KSSV]

You have to mention what you are expecting actually?

[Atinesh Singh]

I need to check whether a particular element present in the population If it does then I want to remove it from the population

Answer 1

[KSSV]

idx = 1:length(P) ;
P  = P(find(idx ~= xi));

[Atinesh Singh]

Its not working "I need to check whether a particular element present in the population If it does then I want to remove it from the population"

[KSSV]

Your xi is [1 1 1]..P has indices [1 2 3]. [1] is common with xi and P, so the above code picks up only [2 3] indices of P.

[Atinesh Singh]

Population has two row Position and cost. Lets say I have a population initialized as (Position; Cost) (1 1 1; 3) (2 2 2; 12) (3 3 3; 27)

Say xi = (2 2 2) #Position

As it is in the population then member corresponding to it should be removed from the population. New population should be

(1 1 1; 3) (3 3 3; 27)

[KSSV]

Pos = reshape([P.Position] ,3,[])' ;
[val,idx] = ismember(xi,Pos,'rows') ;
pick = setdiff(1:length(P),idx) ;
iwant = P(pick) ;

[Atinesh Singh]

is there any other way to do it

[KSSV]

Define xi as a structure..And try using ismemeber etc.