topic Re: SAS loses decimal accuracy in SAS Enterprise Guide

SAS loses decimal accuracy

Dontik — Thu, 26 Oct 2017 16:33:56 GMT

Hi

I have a weird problem. I am operating on numbers which add up to around 800 000 000. I have a dataset which I need to split into minidatasets with 1000 000 records. The problem is that when I split my dataset, I loose decimal precision, for example:

Befote splitting the sum of my costs was 810268311.8536920

After splitting - 810268311.8401380

Splitted datasets have the total number of records equal to number of records which was in the initial table.

What can I do about that?

Thank you in advance!

Re: SAS loses decimal accuracy

TomKari — Thu, 26 Oct 2017 16:36:29 GMT

Your numbers never had the accuracy. The 8 byte floating point numeric format used by SAS can only hold up to fifteen significant digits accurately. Your numbers have sixteen digits; you will lose precision on the sixteenth and above digits.

Tom

Re: SAS loses decimal accuracy

Dontik — Thu, 26 Oct 2017 16:51:13 GMT

Hmm so what is there to do about that? Can I at least keep the number at 0.01 decimal precision? 810268311.85 - so that I could get this exact number after splitting, I do not need anything more precise. I"ve tried adding round(cost,0.01) to my data step which splits the data but that didn't help.

Re: SAS loses decimal accuracy

ChrisHemedinger — Thu, 26 Oct 2017 17:01:51 GMT

There is an exhausting treatise on this topic here:

Numerical precision in SAS

The behavior of SAS is the same as any software that relies on floating point math, defined by an IEEE standard.

There is a newer DECIMALCONV= option that might help. From the doc:

DECIMALCONV=STDIEEE

specifies to convert and format decimal values by using the IEEE Standard for Floating-Point Arithmetic 754-2008. Using the STDIEEE argument improves the accuracy and readability of floating-point numbers. In some cases, more significant digits can be displayed in the same field width.

Re: SAS loses decimal accuracy

Dontik — Thu, 26 Oct 2017 17:15:40 GMT

Unfortunately, my SAS says "unrecognized SAS option name, DECIMALCONV" 😕

Re: SAS loses decimal accuracy

ChrisHemedinger — Thu, 26 Oct 2017 17:19:53 GMT

DECIMALCONV= was added in SAS 9.4.

Re: SAS loses decimal accuracy

Astounding — Thu, 26 Oct 2017 17:33:57 GMT

To the extent you can work with integers instead of decimal fractions, the results will improve. If it would be practical, try:

Multiply costs * 1000
Sum up the new costs
Divide the totals by 1000

Those totals should be closer.