Use array values as assignment indecis

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Gabriel Stanley 2022-11-23

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https://ww2.mathworks.cn/matlabcentral/answers/1861008-use-array-values-as-assignment-indecis

评论： Matt J 2023-5-8

采纳的回答： Matt J

在 MATLAB Online 中打开

A = N-by-2 array, wherein A(:,1)<A(:,2)

B = M-by-2 array, wherein B(:,1)<B(:,2)

A and B are essentially time stamps.

C = unique(vertcat(A,B));

[~,D] = ismember(A,C);

[~,E] = ismember(B,C);

C([D(1,1):D(1,2),...D(N,1):D(N,2)],2) = any scalar, or an array with a sufficient number of elements to dstribute.

C([E(1,1):E(1,2),...E(N,1):E(N,2)],3) = any scalar, or an array with a sufficient number of elements to dstribute.

I'm hung up on defining those assignment indecis [D(1,1):D(1,2),...D(N,1):D(N,2)] without using a loop, i.e.

IdcsD = double.empty;
for i=1:size(D,1)
    Idcs = [Idcs,[D(i,1):D(i,2)]];
end
C(IdcsD) = Value;

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Matt J 2022-11-23

Please show an example for small N and showing the desired output D.

Gabriel Stanley 2022-11-23

编辑：Gabriel Stanley 2022-11-23

Value is a scalar, while OBE

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采纳的回答

Matt J 2022-11-23

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1861008-use-array-values-as-assignment-indecis#answer_1110013

编辑：Matt J 2022-11-23

在 MATLAB Online 中打开

The question has nothing to do really with ismember. It's more about how to turn a list of interval end points into indices. One way is as follows:

D=[1 5 9;
   2 7 12]'  %interval end points
D = 3×2
     1     2
     5     7
     9    12
C=rand(1,12);  
nc=length(C);
assert(all(diff(D,1,2)>=0)   & all(D(:)>0)  & all(D(:)<=nc) ,'Invalid data present')
D=D+[0,1];  s=0*D+[1,-1];
csum=cumsum( accumarray(D(:),s(:),[nc+1,1]) );
Idcs=logical(csum(1:end-1))',
Idcs = 1×12 logical array
   1   1   0   0   1   1   1   0   1   1   1   1
Idcs=find(Idcs) %Shouldn't be needed. Use logical indices above.
Idcs = 1×9
     1     2     5     6     7     9    10    11    12

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Gabriel Stanley 2023-5-8

So in the case of the interval end points of D defining a subset of some larger data set C, nC should be set to the maximum index of the relevant dimension in C?