A Quickie: do I have to create a temp array in my code

Question

Scragmore 2011-11-28

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Hi,

Q? do I have to create the temp array 'abMt'. Can I rap 'TxTRIn{ii,2}(indx,2:5)' in max to get ans?

first I create an index of the section of the array I wish to find max
load required data into temp array
max(array(:)) returns absolute max for complete data set.
  indx = (TxTRIn{ii,2}(:,1)>= 800) & (TxTRIn{ii,2}(:,1)<= 1500);
  abMt = TxTRIn{ii,2}(indx,2:5);
  abMax = max(abMt(:));

Thanks

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Answer 1

David Young 2011-11-28

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It looks as if TxTRIn{ii,2}(indx,2:5) is 2D. If that's correct, you can write

abMax = max(max(TxTRIn{ii,2}(indx,2:5)));

to avoid the temporary array. However, the way you have it now is probably clearer to read, and I doubt that it is any less efficient.

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Scragmore 2011-11-28

FYI,

looks like I am sticking with the temp array. over 1000 cycles of my function the times came in 21sces for max(max()) and 17secs for max(temp_array(:))

AD

Walter Roberson 2011-11-28

And for max(reshape(...)) ?

There isn't much overhead for creating a temporary variable to store something that is already calculated. The overhead comes if you modify the temporary array. Using (:) to reshape to a column vector does not require modifying the temporary array, just creating a header with the dimensions changed but pointing to the same data block.

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