need help for take data from loop

Question

christiano doni 2015-4-6

评论： christiano doni 2015-4-6

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 2015-4-6

编辑：Philipp Maier 2015-4-6

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);

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

Answer 2

Jan 2015-4-6

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 .