Fill a zeros matrix with another matrix until it is full

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Davidra Fantarina ANDRIAMISAINA 2018-2-5

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https://ww2.mathworks.cn/matlabcentral/answers/380795-fill-a-zeros-matrix-with-another-matrix-until-it-is-full

评论： Sumara 2019-6-14

I want to fill the array essai with the value in the array key but my code return zeros

k= 1:length(key);
yr=reshape(y.',1,[]);
essai=zeros(1,length(yr));
essai=uint8(essai);
for n= 1:length(essai)
   if k <length(key)
essai(n)=essai(n)+key(k)
else if k== length(key)
    essai(n)=essai(n)+key(k);
     k=1;
     end
     end
 end

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Stephen23 2018-2-5

编辑：Stephen23 2018-2-5

@Davidra Fantarina ANDRIAMISAINA: your code is very badly aligned. Badly aligned code is how beginners hide simple bugs and logical errors in their code. You should use the default alignment of the MATLAB editor: select the code and press ctrl+i.

Sumara 2019-6-14

THANK YOU! I've wanted to do this for when my code became misaligned but didn't know there was a command for it and fixing manually is so tedious !!!

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Answer 1

Stephen23 2018-2-5

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https://ww2.mathworks.cn/matlabcentral/answers/380795-fill-a-zeros-matrix-with-another-matrix-until-it-is-full#answer_303492

编辑：Stephen23 2018-2-5

在 MATLAB Online 中打开

MATLAB is not an ugly low-level language like C++ and does not need loops to solve all tasks:

idx = 1+mod(0:numel(y)-1,numel(key));
essai = uint8(key(idx));

And tested on some random data:

>> y = 0:9;
>> key = 2:2:8;
>> idx = 1+mod(0:numel(y)-1,numel(key));
>> essai = uint8(key(idx))
essai =
  2  4  6  8  2  4  6  8  2  4

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Davidra Fantarina ANDRIAMISAINA 2018-2-5

Thanks, it works but can you explain this idx thing please

Stephen23 2018-2-5

编辑：Stephen23 2018-2-5

在 MATLAB Online 中打开

"but can you explain this idx thing please"

idx is a vector of indices. Lets look at my example data:

>> y = 0:9 % a vector with ten elements.
y =
   0   1   2   3   4   5   6   7   8   9
>> key = 2:2:8 % a vector with four elements.
key =
   2   4   6   8
>> idx = 1+mod(0:numel(y)-1,numel(key)) % index vector
idx =
   1   2   3   4   1   2   3   4   1   2
>> key(idx) % use the indices
ans =
   2   4   6   8   2   4   6   8   2   4

You can see how the idx values are 1 to 4 repeated up until the vector has the same number of indices as y has elements: these indices determine which elements of key will get selected: so the output vector is equivalent to

[key(1),key(2),key(3),key(4),key(1),key(2),key(3),...]

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