I need help with my While Loop!

Question

Uma Dixit 2020-2-23

0
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评论： darova 2020-2-26

I have an original array (3D) called 'pixelArray' that I eventually need to crop 3 different ways. So I have 3 different sets of x1,x2,y1,y2 numbers that crop the original array in different ways.

I currently have it set up like this:

 x1 = [52, 52, 52];
 x2 = [480, 480, 480];
 y1 = [4, 1, 205] ;
 y2 = [392, 205, 392];
n = 1;
while n < 3
    %crop rows
    pixelArray(1:y1(n),:,:)=[];
    pixelArray(y2(n):end,:,:) = [];
    %crop columns
    pixelArray(:,1:x1(n),:)=[];
    pixelArray(:,x2(n):end,:)=[];
    n =n+1;
end

But I want to save each iteration's new pixelArray as its own matrix. What is the best way to go about doing this?

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Uma Dixit 2020-2-26

Oh, very good point. How do you suggest I make sure the original pixelArray matrix stays intact in its dimensions?

darova 2020-2-26

在 MATLAB Online 中打开

Remove elements from the end?

>> a = 1:10
a =
  Columns 1 through 9
     1     2     3     4     5     6     7     8     9
  Column 10
    10
>> a(7:9) = []
a =
     1     2     3     4     5     6    10
>> a(1:3) = []
a =
     4     5     6    10

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Answer 1

Jakob B. Nielsen 2020-2-24

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编辑：Jakob B. Nielsen 2020-2-24

在 MATLAB Online 中打开

Index them! Either as a structure, or an array with a 4th dimension. I personally favour structures, since 4D data makes my head hurt ;) dot indexing is great for looping results.

Also note that you will only get 2 runs of your loop, as after the 2nd run n will equal 3, and your loop terminates before running a 3rd time since the condition is less than 3. Either make the condition less than or equal to 3, or you can use a for loop instead, as your while loop is essentially a for loop where you do the counting yourself - something you dont need to do in this case.

for n=1:3
    %crop rows
    pixelArray(1:y1(n),:,:)=[];
    pixelArray(y2(n):end,:,:) = [];
    %crop columns
    pixelArray(:,1:x1(n),:)=[];
    pixelArray(:,x2(n):end,:)=[];
    Crops(n).pixelArray=pixelArray; 
end