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

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?

1 first I create an index of the section of the array I wish to find max
2 load required data into temp array
3 max(array(:)) returns absolute max for complete data set.

1    indx = (TxTRIn{ii,2}(:,1)>= 800) & (TxTRIn{ii,2}(:,1)<= 1500);
2    abMt = TxTRIn{ii,2}(indx,2:5);
3    abMax = max(abMt(:));

Thanks

Answer 1

[David Young]

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.

[Scragmore]

Thanks

Dave wins by what looks like seconds. Will certainly test the timing on this.

Thank again both of you.

AD

[Scragmore]

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]

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.

Answer 2

[Walter Roberson]

max(TxTRIn{ii,2}(indx,2:5)) is valid syntax, but it would give one maximum per column rather than an overall maximum.

It is not allowed use TxTRIn{ii,2}(indx,2:5)(:)

It is, though, allowed to use reshape(TxTRIn{ii,2}(indx,2:5),[],1)

[Scragmore]

FYI,

max(reshape(...)) came out consistently at 21secs.

max(temp_array(:)) it is then.