Finding equal values in two matrices and create a new matrix

Hello,

how can I find equal values in two matrices and create a new matrix?

More precise:

I have two .txt files 'Particles' and 'Fragments' (see attachement).

I want to assign the IDs of the Fragments (column 1 in 'Fragments.txt') to the cartesian coordinates of the respective particle from which they emerged from (columns 9-11 in 'Particles.txt') by finding the motherID of the particles (column 2 in 'Particles.txt') in the 'Fragments.txt' (column 6 in 'Fragments.txt').

In addition to that I want to create a matrix that contains the fragment IDs in the first column and the respective coordinates of the Particles from which their emerged from in columns 2-4.

My first attempts:

clear all
clc

A1 = importdata('Particles.txt');
A2 = importdata('Fragments.txt');

ID_Particles = A1(:,2);
MID_Fragments = A2(:,6);
CooParticles = A1(:,9:11);

[a,b] = ismember(MID_Fragments,CooParticles,'rows');

% c = ismember(ID_Particles,MID_Fragments,'rows');
% I = find(c);
% 
% if ismember(ID_Particles,MID_Fragments)
%     
%     disp(CooParticles)
% 
% end

[Paul]

Hi David,

thank you, that's exactly what I wanted to have.

Answer 1

[David Hill]

A1 = importdata('Particles.txt');
A2 = importdata('Fragments.txt');
ID_Particles = A1(:,2);
MID_Fragments = A2(:,6);
CooParticles = A1(:,9:11);
newMatrix=zeros(size(A2,1),4);
newMatrix(:,1)=A2(:,1);
for k=1:length(ID_Particles)
    a=MID_Fragments==ID_Particles(k);
    newMatrix(a,2:4)=repmat(CooParticles(k,:),nnz(a),1);
end