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dpb
Posts:
8,559
Registered:
6/7/07


Re: numel or length, which is better?
Posted:
Apr 16, 2013 3:16 PM


On 4/16/2013 2:03 PM, Hesham Ismail wrote: > A=magic(4) > length(A) > numel(A) > > length calculate the number of column whereas numel calculate the number > of element ...
Not necessarily...
>> B=rand(3,5); >> length(B) ans = 5 >> C=B'; >> length(B) ans = 5 >> size(B) ans = 3 5 >> size(C) ans = 5 3 >>
As noted in earlier response LENGTH() is max(size(x)) for any x whereas NUMEL() is prod(size(x))
If one is interested in rows or columns (and often are) then have to ask for the size of the pertinent dimension to be certain. Often (input files for a good example) the number of rows is greater than the number of columns, but it isn't always so.
Many years ago there was a bug in a ML function (INTERP1) that got confused over the problem by internally making the assumption that was so and would interpolate across multiple datasets instead of within if there were more interpolants than the length of the interpolating tables per variable.




