Increase efficiency of nested loops that use str2double and datenum functions?

[Jared Stofflett]

The following code operates on a cell matrix obtained using the sqlite3  
package. It takes several minutes to run with a matrix containing about  
20000
rows. The bottlenecks appear to be the datenum and str2double  
functions. Any help on increasing it's efficiency would be appreciated.

DJI2=0;
for i=1:length(DJI)
DJI2(i,1)=datenum(char(DJI(i,2)),'yyyy-mm-dd');
for j=3:7
DJI2(i,j-1)=str2double(char(DJI(i,j)));
end
end