How to separate vector into vectors of different lengths

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Md Shahriar Islam 2018-10-12

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https://ww2.mathworks.cn/matlabcentral/answers/423578-how-to-separate-vector-into-vectors-of-different-lengths

评论： Md Shahriar Islam 2018-10-12

I have a vector y=[1:1:10] and length vector l=[2,5,10] % these are the sample number of the vector y; I want to separate the y vector so that y1=[1,2]; y2=[3,4,5]; y3=[6,7,8,9,10];

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Stephen23 2018-10-12

编辑：Stephen23 2018-10-12

Uh ... facepalm

Thank you Star Strider. If I had looked I would have saved myself reinventing the wheel :)

Star Strider 2018-10-12

My pleasure, Stephen. I posted my Answer 6 days (and 1115 Questions) before this one, so it would have been difficult to find.

I probably should have made my explanation a bit more obvious, and emphasized that ‘Out’ was the desired result, although I thought it would be self-explanatory as I posted it.

Live and learn!

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KSSV 2018-10-12

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https://ww2.mathworks.cn/matlabcentral/answers/423578-how-to-separate-vector-into-vectors-of-different-lengths#answer_341012

在 MATLAB Online 中打开

y=[1:1:10] ;
l=[2,5,10] ;
y1=[1,2] ;
y2=[3,4,5] ;
y3=[6,7,8,9,10] ;
iwant = cell(length(l),1) ;
iwant{1} = y(1:l(1)) ;
for i = 2:length(l)
    iwant{i} = y(l(i-1)+1:l(i)) ;
end

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Md Shahriar Islam 2018-10-12

This works fine. But facing an issue with the actual data when I have a situation of similar to l=[2,5,9] here I would like to collect data in between the lengths 2to5; 5to9; and 9to10

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Stephen23 2018-10-12

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https://ww2.mathworks.cn/matlabcentral/answers/423578-how-to-separate-vector-into-vectors-of-different-lengths#answer_341017

编辑：Stephen23 2018-10-12

在 MATLAB Online 中打开

The simple MATLAB way:

>> y = 1:10;
>> x = [2,5,10];
>> c = mat2cell(y,1,diff([0,x]));
>> c{:}
ans =
    1    2
ans =
    3    4    5
ans =
    6    7    8    9   10

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Stephen23 2018-10-12

编辑：Stephen23 2018-10-12

在 MATLAB Online 中打开

@Md Shahriar Islam: when I run your code the only error is due to xx being a column vector (again this is unlike your question, where it is a row vector). This is also trivial to fix:

dd = diff([0;xx(:);numel(yy)]);

Giving code that runs without any error:

>> dd = diff([0;xx(:);numel(yy)]);
>> cc = mat2cell(yy(:),dd,1);
>> num = cellfun(@numel,cc)
num =
      445672
      119018
      134472
      107560
      102999
      127632
      265177
      128830
      115453
      191299
>> sum(num)
ans =
     1738112

But I suspect that your entire algorithm is fundamentally flawed: If you are trying to detect the moment of "impact", then simply removing a fixed number of trailing idx elements might not work. Consider this example:

ind  = [ 0, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 1] % abs(..)>thresh
tvec = [ 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,15,16]
idx = ???

Lets assume that t_min is 6: what are the indices that you would expect to have in the output idx ?:

idx=[3,9,15] 6-second steps, any 1 in a group allowed.
idx=[3,15] Only the first 1 in each group is permitted.
idx=[???] Something else? Please explain what and why.

Stephen23 2018-10-12

编辑：Stephen23 2018-10-12

@Md Shahriar Islam: You missed my point. The question is: do you want the values in idx to represent the first 1 in a sequence of 1's, or do you want to detect any 1 in a sequence of 1's?

The same question in different words: what are the indices in idx supposed to represent? Are they supposed to represent the start of each "impact".

Please read my previous comment again, and tell my what indices you would expect for the small example I gave. This is very important to know exactly what you mean when you say that you want "to separate impacts".

Md Shahriar Islam 2018-10-12