The following loop takes about 700 seconds to run in octave and 22 seconds to run in matlab when the DJI matrix has 21000 rows. How can I increase the efficiency of this?
for i=1:length(DJI) DJI2(i,1)=datenum(char(DJI(i,2)),'yyyy-mm-dd'); end
views:
369answers:
2
+1
A:
Did you remember to preallocate DJI2?
More importantly, you do not need the loop at all. datenum operates on arrays.
Try this:
DJI2=datenum(char(DJI(:,2)),'yyyy-mm-dd');
Dima
2008-12-08 19:53:57
Using char() does not seem to allow me to call datenum on the entire array, the code example you gave doesn't work.
Jared
2008-12-08 23:18:48
What is the type of DJI? Is it a cell array? If you have an array A = ['2005-10-10'; '2006-11-12'; ...] then datenum(A, 'yyyy-mm-dd') will work. See if you can convert DJI to something that looks like A.
Dima
2008-12-09 19:07:37
+1
A:
I replaced the loop with the following and got at least a one order of magnitude increase in speed.
DJI2(:,1) = reshape(datenum(strvcat(DJI(:,2)(:)), length(DJI(:,2)),'yyyy-mm-dd'));
Jared
2008-12-08 23:17:18