why? get the chg value -0.2999999999? how to modify it?

[blueskyxyz]

chg=aval- base;

....

run;

why? get the value -0.2999999999? how to modify it?

[PaigeMiller]

SAS (and all computer software) stores numbers in a binary form, and so some decimal values cannot be represented exactly, this is not possible and not avoidable.

However, you can change the way the numbers are displayed, so if you assign a format to CHG, then it displays with one decimal place. For example:

format chg 8.1;

[blueskyxyz]

Miller, thanks for your answer, there are different parameters with different digitals, it is not good to use format to change all param.

[Patrick]

The root cause is how computers store numbers. Details here.

And here some coding options for dealing with it.

data test;
  aval=51.6;
  base=51.9;
  chg=aval-base;
  chg1=round(aval-base,.0000000001);
  chg2=aval-base;
  chg3=sum(aval,-base);
  format chg2 best32.1;
run;
proc print data=test;
run;