topic Re: Exponential code in SAS Programming

Exponential code

ursula — Mon, 10 Apr 2023 20:17:45 GMT

Hi,

Anyone can help me of how to code the below equation into SAS:

another one is (1e-6), how to code it in SAS?

Thanks in advance.

Re: Exponential code

Reeza — Mon, 10 Apr 2023 20:22:01 GMT

EXP function for the e

** is power operator so for 2^3 you can do 2**3

@ursula wrote:

Hi,

Anyone can help me of how to code the below equation into SAS:

another one is (1e-6), how to code it in SAS?

Thanks in advance.

Re: Exponential code

ballardw — Mon, 10 Apr 2023 22:34:01 GMT

The 1E-6 is easy in SAS: That is acceptable as a fixed value though there might sometimes be some issues related to storage precision. The FORMAT you use to display the value might be of interest.

data example;
   file print;
   x=1E-6;
   put 'Best5. format' x= best5.;
   put '9.7 format '   x= 9.7;
run;

Since you have the same long exponent in the numerator and denominator I would suggest calculating that as another variable and have much simpler code to type like

FAST = exp(thatvar)/ (1+Exp(thatvar));

Re: Exponential code

s_lassen — Tue, 11 Apr 2023 07:19:17 GMT

The formula can be calculated in a single step, but as the same complex expression occurs twice, it is faster to calculate it in two steps:

FAST=exp(-1.65+1.07*log(LSM)+2.66E-8*CAP**3-63.3/AST);                                                                                
FAST=FAST/(1+FAST);

- by "faster" I mean both the amount of typing to be done, and the CPU time for the calculation.

Re: Exponential code

FreelanceReinh — Tue, 11 Apr 2023 10:56:02 GMT

Hi @ursula,

You can also use the LOGISTIC function to make the code shorter:

FAST=logistic(-1.65+...);