topic Re: Programing Contrast Statment for 4x2 factorial design in Statistical Procedures

Programing Contrast Statment for 4x2 factorial design

Maicon — Thu, 11 Nov 2021 12:05:33 GMT

Hello!
How can I program the CONTRAST statment for decomposition of a 4x2 interaction by using linear and quadratic contrasts? The SAS code I'm performing just shown the main component "NIVEL" contrast.

proc glimmix data=WORK.IMPORT;
Class NIVEL ENZ;
Model CMMS = NIVEL ENZ NIVEL*ENZ/ddfm=kr;
Lsmeans NIVEL*ENZ/ adjust=tukey diff lines;
   contrast 'Linear'     NIVEL -0.67082 -0.223607 0.2236068 0.6708204;
   contrast 'Quadratico' NIVEL 0.5	-0.5	-0.5	0.5;
run;

The significant NIVEL*ENZ interaction should be decomposed in linear and quadratic contrasts of the LEVEL(0; 7.5; 15.0; or 22.5) component into the ENZ(0 or 1) component. Please, if anyone can help me! Thank you very much!

Re: Programing Contrast Statment for 4x2 factorial design

sbxkoenk — Thu, 11 Nov 2021 15:58:14 GMT

Post was moved to statistical_procedures board by me.

Koen

Re: Programing Contrast Statment for 4x2 factorial design

sbxkoenk — Thu, 11 Nov 2021 16:08:58 GMT

Just adding this:

Many contrast and estimate statements can be "avoided" by using :

LSMEANS statement and / or LSMESTIMATE Statement and SLICE Statement.

Please use LSMEANS / LSMESTIMATE / SLICE statements where appropriate.

Should you still need a CONTRAST statement, these blogs may learn you something new :

Usage Note 67024: Using the ESTIMATE or CONTRAST statement or Margins macro to assess continuous variable effects in interactions and splines
67024 - Using the ESTIMATE or CONTRAST statement or Margins macro to assess continuous variable effects in interactions and splines (sas.com)
The magical ESTIMATE (and CONTRAST) statements
By Chris Daman on SAS Learning Post April 23, 2012
https://blogs.sas.com/content/sastraining/2012/04/23/the-magical-estimate-and-contrast-statements/
"Easy button" for ESTIMATE statements
By Chris Daman on SAS Learning Post April 25, 2012
https://blogs.sas.com/content/sastraining/2012/04/25/easy-button-for-estimate-statements/
ESTIMATE Statements - the final installment
By Chris Daman on SAS Learning Post May 2, 2012
https://blogs.sas.com/content/sastraining/2012/05/02/estimate-statements-the-final-installment/
How to write CONTRAST and ESTIMATE statements in SAS regression procedures?
By Rick Wicklin on The DO Loop June 6, 2016
https://blogs.sas.com/content/iml/2016/06/06/write-contrast-estimate-statements-sas-regression-procedures.html
Usage Note 24447: Examples of writing CONTRAST and ESTIMATE statements
https://support.sas.com/kb/24/447.html

Best regards,
Koen

Re: Programing Contrast Statment for 4x2 factorial design

StatDave — Thu, 11 Nov 2021 17:33:28 GMT

If you are saying that you want to assess the linear and quadratic effects of NIVEL and also whether those effects change depending on the level of ENZ, then you are saying that NIVEL is continuous and it can be removed from the CLASS statement. You can then fit the following model to assess the linear and quadratic effects of NIVEL and also their interactions with ENZ:

class enz;

model cmms = nivel nivel*nivel enz enz*nivel enz*nivel*nivel;

Re: Programing Contrast Statment for 4x2 factorial design

SteveDenham — Tue, 16 Nov 2021 14:48:08 GMT

Try this:

proc glimmix data=WORK.IMPORT;
Class NIVEL ENZ;
Model CMMS = NIVEL ENZ NIVEL*ENZ/ddfm=kr;
Lsmeans NIVEL*ENZ/ adjust=tukey diff lines e;
   contrast 'Linear NIVEL at ENZ=0'     NIVEL*ENZ  -3 -1 1 3  0 0 0 0;
   contrast 'Quadratic NIVEL at ENZ=0' NIVEL*ENZ 1 -1 -1 1  0 0 0 0;
   contrast 'Linear NIVEL at ENZ=1'     NIVEL*ENZ  0 0 0 0  -3 -1 1 3;
   contrast 'Quadratic NIVEL at ENZ=0' NIVEL*ENZ 0 0 0 0   1 -1 -1 1;
run;

Since you are using CONTRAST rather than ESTIMATE, you can use integer coefficients. If you want some output value, rather than just a p value, switch to LSMESTIMATE statements.

I added the 'E' option to your LSMEANS statement as a check on the arrangement of coefficients in the CONTRAST statements.

SteveDenham