08-12-2014 02:55 PM
We have an issue where we are adding a supplied number to a starting point number to calculate which observation is selected. The problem is every once in awhile the incorrect observation is selected. I.E. 73946.6 + 8212.4 should equal obs # 82159 but 82158 is selected instead. Is there a way to correct this in SAS?
08-12-2014 03:29 PM
Not sure if I have completely understood your issue. However, the first thing comes to my mind that it might be about precision. Apply round() or ceil() or floor() etc consistently and see if it gets fixed.
08-12-2014 04:20 PM
I have seen this happening more often as result of not understanding what precision (floating point Ieee standard) has as impact.
Calculating and integer from decimal fractions is a bad idea. Just think on the following :
3 * 1/3 =? 1 3 * 0.3 =0.9 ? 3*0,3333 = 0,9999 ? or 1 3*0.333 333 333 333 333 333 =?
The floating point is having about 12 meaningfull digits.