topic Re: how to use absolute function in proc model to solve nonlinear equations in SAS Programming

how to use absolute function in proc model to solve nonlinear equations

tonghui1127 — Sun, 16 Jun 2019 03:10:51 GMT

how to use absolute function in proc model to solve nonlinear equations.

Re: how to use absolute function in proc model to solve nonlinear equations

Kurt_Bremser — Sun, 16 Jun 2019 08:17:32 GMT

@tonghui1127 wrote:

how to use absolute function in proc model to solve nonlinear equations.

Like you use it in a data step, it is the same function.

Re: how to use absolute function in proc model to solve nonlinear equations

tonghui1127 — Sun, 16 Jun 2019 20:26:52 GMT

Dear KurtBremser

Thank you for your rely.

This is my SAS code, when i use proc model to solve pie1 , I think there has some values are negative. So I want to use ABS() function in my formula to make sure there is no negative values. But this is not work.

proc model data = data2 out = data3;
eq.f = (p*t*pie1+(1-p)*(1-t)*(1-pie1)-x1/&NumTrials)
+(p*(1-t)*pie1+(1-p)*t*(1-pie1)-x2/&NumTrials)
+((1-p)*t*pie1+p*(1-t)*(1-pie1)-x3/&NumTrials)
+((1-p)*(1-t)*pie1+p*t*(1-pie1)-x4/&NumTrials);
solve pie1;

proc print data = data3;
run;

This is the result i got after run code, the pie1 is .0001 , i don't know how to fix this problem.

PREDICT	SIMULATE	.0001	0.7	0.7	77	115	86	222
PREDICT	SIMULATE	.0001	0.7	0.7	58	104	117	221
PREDICT	SIMULATE	.0001	0.7	0.7	58	112	111	219
PREDICT	SIMULATE	.0001	0.7	0.7	74	110	109	207
PREDICT	SIMULATE	.0001	0.7	0.7	68	93	125	214
PREDICT	SIMULATE	.0001	0.7	0.7	62	110	95	233
PREDICT	SIMULATE	.0001	0.7	0.7	64	104	113	219
PREDICT	SIMULATE	.0001	0.7	0.7	57	103	94	246
PREDICT	SIMULATE	.0001	0.7	0.7	70	106	114	210

Re: how to use absolute function in proc model to solve nonlinear equations

Kurt_Bremser — Tue, 02 Jul 2019 05:22:31 GMT

If you want to prevent negative values of pie1 in your solution, either set them to zero by using the max() function, eg

max(pie1,0)

instead of just pie1, or use a where condition on the dataset to discard such observations.