BookmarkSubscribeRSS Feed
sysmars
Calcite | Level 5

we want to use this model to calculate the X threshold where Y begin to decline, with conidence interval.

The attached is out data.

who has the procedure? could ou send me a copy? thanks a lot.

2 REPLIES 2
SteveDenham
Jade | Level 19

Carefully look at the documentation for PROC NLIN, especially Example 63.1 Segmented model.  This fits a quadratic up to an unknown join point, followed by a plateau.

title 'Quadratic Model with Plateau';

proc nlin data=a;

  parms alpha=.45 beta=.05 gamma=-.0025;

  

  x0 = -.5*beta / gamma;

  

  if (x < x0) then

  mean = alpha + beta*x + gamma*x*x;

  else mean = alpha + beta*x0 + gamma*x0*x0;

  model y = mean;

  if _obs_=1 and _iter_ =. then do;

  plateau =alpha + beta*x0 + gamma*x0*x0;

  put / x0= plateau= ;

  end;

  output out=b predicted=yp;

run;

I hope this gets you started on what you wish to do.

Steve Denham

sysmars
Calcite | Level 5

Thanks so much Steve, and also, does below procedure can also be used for our data? what the difference between this 2 procedures?

DATA a;

INPUT met gain @@;

DATALINES;

80 102 85 115 90 125 95 133 100 140

105 141 110 142 115 140 120 142

;

PROC NLIN;

PARMS a = 102 b = 2.7 c = -0.04;

x = met-80;

x0 = -.5*b / c;

IF x < x0 THEN

MODEL gain = a+b*x+c*x*x;

ELSE

MODEL gain = a+b*x0+c*x0*x0;

IF _obs_=1 and _iter_ =. THEN DO;

plateau = a+b*x0+c*x0*x0;

x0 = x0+80;

PUT / x0 = plateau= ;

END;

RUN;

and another question is, how to make a graph like below, thanks a lot.

images.jpg

sas-innovate-2024.png

Available on demand!

Missed SAS Innovate Las Vegas? Watch all the action for free! View the keynotes, general sessions and 22 breakouts on demand.

 

Register now!

What is Bayesian Analysis?

Learn the difference between classical and Bayesian statistical approaches and see a few PROC examples to perform Bayesian analysis in this video.

Find more tutorials on the SAS Users YouTube channel.

Click image to register for webinarClick image to register for webinar

Classroom Training Available!

Select SAS Training centers are offering in-person courses. View upcoming courses for:

View all other training opportunities.

Discussion stats
  • 2 replies
  • 3332 views
  • 0 likes
  • 2 in conversation