need help for take data from loop

I have scrip data like this

clear all;close all;clc

c1=imread('1200TIM-20150401-0010_20150401-1054015001500-1','png');

a1=double(c1);

a1=reshape(a1,2229000,[]);

c2=imread('1200TIM-20150401-0020_20150401-1054015001500-1','png');

a2=double(c2);

a2=reshape(a2,2229000,[]);

c3=imread('1200TIM-20150401-0030_20150401-1054015001500-1','png');

a3=double(c3);

a3=reshape(a3,2229000,[]);

and I have matrix

a1=(2229000,3); a2=(2229000,3); a3=(2229000,3);

and i want to make 3 matrix data like this

red=[a1(:,1),a2(:,1),a3(:,1)]

green=[a1(:,2),a2(:,2),a3(:,2)]

blue=[a1(:,3),a2(:,3),a3(:,3)]

*my questions is how to make loop for red, grean and blue because data a1, a2 until a100, i try *

for i=1:1:3; red(:,i)=['a'num2str(i)(:,1)]; end

but its not working here

Answer 1

[Philipp Maier]

The eval function can be used to execute the MATLAB expression. For example:

for i=1:1:3; 
    red(:,i)= eval(['a' num2str(i) '(:,1)'])'; 
end

Since I do not have the PNG-files that you are reading , I tested the code with three random variables:

a1 = rand(2229000,3);
a2 = rand(2229000,3);
a3 = rand(2229000,3);

[christiano doni]

ah ...thank you sir...it's working here

Answer 2

[Jan]

No, do not do this. It might work in this specific case, but it is in general an evil method and it produces more troubles than it solves. The problem is discussed several times a day and therefore you find it in the frequently asked questions also: http://www.mathworks.com/matlabcentral/answers/57445-faq-how-can-i-create-variables-a1-a2-a10-in-a-loop .

See also: http://www.mathworks.com/matlabcentral/answers/51946-systematic-do-not-use-global-don-t-use-eval

[christiano doni]

ok sir, move to you link.. thanks for you advice