Creating new registors using Loop

Question

Ghulam 2018-3-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/389596-creating-new-registors-using-loop

评论： Jan 2018-3-24

Hi, I am writing a code in which a block of code is repeated many times. But for every time the values are saved in new variables which are repeated too. I want that the names of the variables updates automatically like using a loop or something like that.

if true
  % My Code
[R1,R2,R3,R4,F,M1,M2,M3,M4,OG, G1,G2,G3,G4]=fir(); 
[tr,rc,lc,br]=rotatearray(G1);
[tr2,rc2,lc2,br2]=rotatearray(R1);
channel1= M1(:,:,1);
channel2= M1(:,:,2);
channel3= M1(:,:,3);
Zero1 = uint8(zeros(1728));
Zero2 = uint8(zeros(1728));
Zero3 = uint8(zeros(1728));
Zero1([tr2:br2],[lc2:rc2]) = channel1([1:end],[(rc-rc2+1):end]); 
Zero2([tr2:br2],[lc2:rc2]) = channel2([1:end],[(rc-rc2+1):end]); 
Zero3([tr2:br2],[lc2:rc2]) = channel3([1:end],[(rc-rc2+1):end]); 
final1 = cat(3,Zero1,Zero2,Zero3);
 %FOR a3
[tr,rc,lc,br]=rotatearray(G2);
[tr2,rc2,lc2,br2]=rotatearray(R2);
 channel1= M2(:,:,1);
 channel2= M2(:,:,2);
 channel3= M2(:,:,3);
  Zero1 = uint8(zeros(1728));
 Zero2 = uint8(zeros(1728));
 Zero3 = uint8(zeros(1728));
Zero1([tr2:br2],[lc2:rc2]) = channel1([(br-br2+1):end],[(rc-rc2+1):end]);
Zero2([tr2:br2],[lc2:rc2]) = channel2([(br-br2+1):end],[(rc-rc2+1):end]);
Zero3([tr2:br2],[lc2:rc2]) = channel3([(br-br2+1):end],[(rc-rc2+1):end]);
final2 = cat(3,Zero1,Zero2,Zero3);
%FOR a4
[tr,rc,lc,br]=rotatearray(G3);
[tr2,rc2,lc2,br2]=rotatearray(R3);
channel1= M3(:,:,1);
channel2= M3(:,:,2);
channel3= M3(:,:,3);
Zero1 = uint8(zeros(1728));
Zero2 = uint8(zeros(1728));
Zero3 = uint8(zeros(1728));
Zero1([tr2:br2],[lc2:rc2]) = channel1([(br-br2+1):end],[1:(end-lc2+1)]); 
Zero2([tr2:br2],[lc2:rc2]) = channel2([(br-br2+1):end],[1:(end-lc2+1)]);  
Zero3([tr2:br2],[lc2:rc2]) = channel3([(br-br2+1):end],[1:(end-lc2+1)]);  
final3 = cat(3,Zero1,Zero2,Zero3);
  end

From here you can have the idea that most of the block of code is same just the input register (M 1,2,3) is changing, So can how can we select the input register automatically. I have tried using a loop but it didn't work.

Kindly guide me about it.

Regards

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Stephen23 2018-3-21

编辑：Stephen23 2018-3-21

"I want that the names of the variables updates automatically like using a loop or something like that"

Dynamically accessing variable names is how beginners force themselves into writing slow, complex, buggy code that is hard to debug. The MATLAB documentation specifically recommends against dynamically accessing variable names: "A frequent use of the eval function is to create sets of variables such as A1, A2, ..., An, but this approach does not use the array processing power of MATLAB and is not recommended. The preferred method is to store related data in a single array."

source: https://www.mathworks.com/help/matlab/matlab_prog/string-evaluation.html

All MATLAB experts will also advise you to use one array and indexing. Indexing is simple, neat, easy to debug, and very efficient. When you put a number on the end of variable names then you are using de-facto indexing, so why not simply turn it into real indexing? Then your code will immediately be faster, simpler, less buggy, and easier to debug.

Read this to know more:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Jan 2018-3-24

@Ghulam: Please do not use flags to post a comment. Flagging is used to call the admins for cleaning up a message due to spam or rudeness. Use comments instead.

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Answer 1

Jan 2018-3-21

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/389596-creating-new-registors-using-loop#answer_311064

编辑：Jan 2018-3-21

在 MATLAB Online 中打开

Do not create variables dynamically. See Tutorial: Avoid EVAL . So the answer to

I want that the names of the variables updates automatically

is: Don't do this. Use a multi-dimensional array instead, if all arrays have the same size and type. Otherwise use a cell array.

[R{1},R{2},R{3},R{4},F,M{1},M{2},M{3},M{4},OG, ...
 G{1},G{2},G{3},G{4}] = fir(); 
final = cell(1, 4);
for k = 1:4
  [tr,rc,lc,br]=rotatearray(G{k});
  [tr2,rc2,lc2,br2]=rotatearray(R{k});
  channel1 = M{k}(:,:,1);
  channel2 = M{k}(:,:,2);
  channel3 = M{k}(:,:,3);
  Z        = zeros(1728, 1728, 3, 'uint8');
  Z(tr2:br2, lc2:rc2, 1) = channel1(:, (rc-rc2+1):end); 
  Z(tr2:br2, lc2:rc2, 2) = channel2(:, (rc-rc2+1):end); 
  Z(tr2:br2, lc2:rc2, 3) = channel3(:, (rc-rc2+1):end); 
  final{k} = Z;
end

Or even shorter:

[R{1},R{2},R{3},R{4},F,M{1},M{2},M{3},M{4},OG, ...
 G{1},G{2},G{3},G{4}] = fir(); 
final = cell(1, 4);
for k = 1:4
  [tr,rc,lc,br]     = rotatearray(G{k});
  [tr2,rc2,lc2,br2] = rotatearray(R{k});
  Z                 = zeros(1728, 1728, 3, 'uint8');
  Z(tr2:br2, lc2:rc2, :) = M{k}(:, (rc-rc2+1):end, :);
  final{k} = Z;
end