Strange result using lt comparison operator

[SP_SAS]

Hi There,

If I run the below data step I see SAS behaving in strange manner. Variable y resolves to 1.2. SAS thinks x(1.2) is less than y. Any help will be appreciated.

Thanks,

Santosh

data aa;

x=1.2;
y=(1.1+1*0.1);
if x<y then Confused="Yes";
else Confused="No";
run;

[PGStats]

SAS numbers are represented internally by floating point values. 1.2 doesn't have an exact representation as a floating point number, so its internal value is an approximation. That approximation will take different values depending on how it was arrived at. Add the following statements and see what happens

if round(x, 0.1) < round(y, 0.1) then RoundConfused="Yes";

else RoundConfused="No";

PG

[Tom]

Use the HEX16. format to look at how these two different numbers end up getting stored into the 8 byte IEEE floating point format.

data aa;

x=1.2;

y=(1.1+1*0.1);

put  (x y) (= hex16. /) ;

x=round(x,0.1);

y=round(y,0.1);

put / (x y) (= hex16. /) ;

run;

x=3FF3333333333333

y=3FF3333333333334

x=3FF3333333333333

y=3FF3333333333333

run;

[ChrisNZ]

Much reading available on this topic.

For example:

Numerical Accuracy in SAS Software: SAS(R) 9.4 Language Reference: Concepts, Fifth Edition

[SP_SAS]

Thanks to you all for your quick help.

Santosh