How to extract elements form a vector in order to create an unknown number of sub-vectors?

Question

Paolo Ottonelli 2020-1-5

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https://ww2.mathworks.cn/matlabcentral/answers/499004-how-to-extract-elements-form-a-vector-in-order-to-create-an-unknown-number-of-sub-vectors

评论： Paolo Ottonelli 2020-1-5

Hello, I have a vector called M, in which there are several numbers. I need to divide it in some sub vectors (y) of different size without changing the order of the data in M. The subvector ends when it is reached a number lower than the previous. this one is the first number of the next subvector

M=[2.24;2.28;2.31;0.99;1.44;1.44;1.44;1.44;
    2.12;2.25;2.48;3.61;1.86;1.89;1.89;1.89;1.89;1.89;1.89];
for j=1:(length(M(:))-1)
if M(j)>M(j+1)
else      y(j)=M(1:j);
 end
end

Finally I should obtain the following vectors but the code doesn't work

y1=[2.24;2.28;2.31]

y2=[0,99;1.44;1.44;1.44;1.44;2.12;2.25;2.48;3.61]

y3=[1.86;1.89;1.89;1.89;1.89;1.89;1.89];

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Answer 1

Stephen23 2020-1-5

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https://ww2.mathworks.cn/matlabcentral/answers/499004-how-to-extract-elements-form-a-vector-in-order-to-create-an-unknown-number-of-sub-vectors#answer_408762

编辑：Stephen23 2020-1-5

在 MATLAB Online 中打开

Here is one simple approach based on diff, cumsum, and accumarray:

>> M = [2.24;2.28;2.31;0.99;1.44;1.44;1.44;1.44;2.12;2.25;2.48;3.61;1.86;1.89;1.89;1.89;1.89;1.89;1.89];
>> X = cumsum([true;diff(M(:))<0]);
>> C = accumarray(X,M(:),[],@(v){v});
>> C{:}
ans =
2400
2800
3100
ans =
99000
44000
44000
44000
44000
12000
25000
48000
61000
ans =
8600
8900
8900
8900
8900
8900
8900