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

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Paolo Ottonelli
Paolo Ottonelli 2020-1-5
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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Stephen23
Stephen23 2020-1-5
编辑：Stephen23 2020-1-5
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 =
2.2400
2.2800
2.3100
ans =
0.99000
1.44000
1.44000
1.44000
1.44000
2.12000
2.25000
2.48000
3.61000
ans =
1.8600
1.8900
1.8900
1.8900
1.8900
1.8900
1.8900
You can access the contents of the cell array using indexing:
https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html
Using numbered variables is unlikely to be a good approach.

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