topic Re: Can SAS Numeric 8 bytes support BEST32.8? in SAS Programming

Can SAS Numeric 8 bytes support BEST32.8?

StickyRoll — Mon, 03 May 2021 09:17:25 GMT

I am new to SAS Programming. Recently my laptop has been formatted and I am still waiting for my IT Team to give me a new SAS installation. Since I have no access to SAS environment, I have a question here.

Assuming the source (load from csv) has numeric column that has numeric with 32 length and 8 decimal places. For example:

123,456,789,012,345,678,901,234,567,890,12.99995555

I want to store the column as numeric because it will be used as a calculation in the next step. Understand that SAS numeric will only supports 8 bytes which translate to max 15 numeric length. Will it work if the numeric length remained 8 bytes but format it as BEST32.8?

I hope i learn something here. Appreciate your effort in explaining.

Re: Can SAS Numeric 8 bytes support BEST32.8?

FreelanceReinh — Mon, 03 May 2021 18:56:41 GMT

Hello @StickyRoll and welcome to the SAS Support Communities!

No, this won't work. Once you've lost the 40-digits precision by storing the value in an 8-byte numeric variable (typically resulting in a precision of 15-16 decimal digits) there is no way to recover it from that variable. Formats just control how a value is displayed. Also note that the BEST32.8 format (edit: which is actually the BEST32. format) has a total length of 32 characters including the decimal places, the decimal point, a minus sign (if any) and exponential notation (if needed). To avoid loss of information you will need to store the number in a character variable (of sufficient length) and use advanced techniques to perform the "calculation in the next step."

Addendum:

@StickyRoll wrote:

For example:

123,456,789,012,345,678,901,234,567,890,12.99995555

The binary floating-point representation of this number would require (at least) 129 mantissa bits in order to achieve sufficient precision, but only 52 are available in an 8-byte numeric variable under Windows and Unix (see Numerical Accuracy in SAS Software).

Re: Can SAS Numeric 8 bytes support BEST32.8?

ChrisNZ — Tue, 04 May 2021 02:50:09 GMT

> Will it work if the numeric length remained 8 bytes

To add a brick to the building of knowledge provided by @FreelanceReinh , it depends on what you mean by "work"

SAS can store numbers up to 1e308, like any 8-byte-storing program on PC/Unix platforms (mainframes are different).

So yes it will work and you can perform calculations, but precision will be lost. Only the first 15 digits will be exact.

Re: Can SAS Numeric 8 bytes support BEST32.8?

SASKiwi — Tue, 04 May 2021 03:13:22 GMT

What real world metric does this represent? The number of stars in the universe? The number of atoms that make up the Earth? Total USA debt? 😉

Re: Can SAS Numeric 8 bytes support BEST32.8?

ChrisNZ — Tue, 04 May 2021 03:25:56 GMT

Don't laugh @SASKiwi we are all paying that debt.

Re: Can SAS Numeric 8 bytes support BEST32.8?

StickyRoll — Wed, 19 May 2021 06:31:47 GMT

Hi everyone,

If i understand correctly, SAS Numeric can only store the precision up to 15 digits.

For example:

123,456,789,012.987

123,456,789,0.98765

123,456,78.9876543

The type is best32..

Re: Can SAS Numeric 8 bytes support BEST32.8?

Kurt_Bremser — Wed, 19 May 2021 07:10:02 GMT

The type can only be character or numeric.

The length of a numeric variable can be between 3 and 8 (on z/OS mainframes 2 and 😎

The format determines how the value is displayed, it does not have an influence on the precision or the minimum/maximum value that can be stored.

And yes, with 8 bytes floating point a maximum of 15 decimal digits can be represented reliably. And, when working with decimal fractions, you will quickly find out that there are a lot of them that result in periodic numbers (infinite number of binary digits) when represented as binary, so you will always have rounding errors there.