How to immediately pick an index from a result that is a matrix.

Question

Roy Veldhuizen 2012-7-3

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https://ww2.mathworks.cn/matlabcentral/answers/42613-how-to-immediately-pick-an-index-from-a-result-that-is-a-matrix

I have a small issue which I stumble upon quite often.

Is it possible to immediately select a certain index if the result is a matrix.

For example, if I have a matrix stored under the Data of a uitable, and i want to retrieve it using get, and then take a certain index from it, my current method is like this:

      para=get(handles.uitable6,'Data');
      Calpha=para(5,1)

However, this requires for the creation of an additional matrix (in this case para), which might increase computing time for very late matrices. Is it possible to immediately pick one of the values from a matrix, thus preventing the creation of an additional matrix.

Thanks in advance,

Roy

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Answer 1

Jan 2012-7-3

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https://ww2.mathworks.cn/matlabcentral/answers/42613-how-to-immediately-pick-an-index-from-a-result-that-is-a-matrix#answer_52429

在 MATLAB Online 中打开

This feature has been requested repeatedly, see: http://www.mathworks.com/matlabcentral/answers/1325#answer_1931

The line

para = get(handles.uitable6,'Data');

does not need a noticable amount of time, becauseit does not crate a new array and copy the data, but it is a "shared copy": only a new header for the variable is created, but the actual data are shared using a pointer to the same memory.

Therefore your posted code is efficient related to memory and processing time. The direct indexing would be "nicer" only.