Reading data in cell arrays help

Question

Albert Rey Ruelan 2017-7-30

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/350835-reading-data-in-cell-arrays-help

回答： Star Strider 2017-7-30

Hi There was this line in a program code.

               for k = 1:9
               [i,j] = ind2sub([3,3],k);
               Output(:,:,indx+k) = AccessImageDiff{row,col}(i:end-3+i,j:end-3+j);
                end

Now my problem is how do i read this line? Can somebody teach me on how to read this specific line

Output(:,:,indx+k) = AccessImageDiff{row,col}(i:end-3+i,j:end-3+j);*

i know that it is accessing a cell array and manipulating its data but what i am confused about is the (i:end-3+i,j:end-3+j) part.

1.what does ":" mean?

2.what does "end" mean? It didn't use end as a variable.

Thanks in advance

There's this tutorial about accessing data in cell arrays but it doesn't really answer my question https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html

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Answer 1

Star Strider 2017-7-30

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https://ww2.mathworks.cn/matlabcentral/answers/350835-reading-data-in-cell-arrays-help#answer_276080

‘... what i am confused about is the (i:end-3+i,j:end-3+j) part.’

Here, end is the size of the array in that dimension. See the documentation on end (link) for a full description, specifically:

The end function also serves as the last index in an indexing expression. In that context, end is the same as size(X,k) when used as part of the kth index into array X. Examples of this use are X(3:end) to select the third through final elements of the array, and X(1,1:2:end-1) to select all even elements of the first row, excluding the last element. When using end to grow an array, as in X(end+1)=5, make sure X exists first.