How to code Physical Activity in NHANES

[abigailpuno]

Hello, 

I am a total newbie in SAS and I'm writing my thesis using the NHANES data. I couldn't quite figure out how to code the physical activity classification and I would really appreciate it if anyone could help me. 

One of my covariate factors is total physical activity and I have referred to the GPAQ (Global Physical Activity Questionnaire) guide from WHO. I matched it with the variables from NHANES codebook and I'm trying to classify it by level of total physical activity. 

The translated variables are the following:

P2 (# of days vigorous work) = paq610

P3 (# of mins vigorous work/day) = pad615

P5 (# of days moderate work) = paq625

P6 (# of mins moderate work/day) = pad630

P8 (# of days walk or bicycle) = paq640

P9 (# of mins walk/bicycle for transportation) = pad645

P11 (# of days vigorous recreational activities) = paq655

P12 (# of mins vigorous recreational activities) = pad660

P14 (# of days moderate recreational activities) = paq675

P15 (# of mins moderate work/day) = pad675

P16 (# of mins sedentary activity) = pad680

I came up with the following code:

/*Physical Activity*/
data demo_dep9; 
	set demo_dep8; 
	/*compute total physical activity or total MET-min/week*/

	totPA=(paq610*pad615*8)+(paq625*pad630*4)+(paq640*pad645*4)+(paq655*pad660*8)+(paq670*pad675*4);
	if (paq610+paq655)>=3 and totPA>=150 or
		(paq610+paq625+paq640+paq655+paq670)>=7 or totPA>=300
	then PAlevel=1; /*High PA Level*/

	if (paq610+paq655)>=3 and ((paq610*pad615)+(paq655*pad660))>=60 or
		(paq625+paq640+paq670)>=5 and ((paq625*pad630)+(paq640*pad645)+(paq670*pad675))>=150 or
		(paq610+paq625+paq640+paq655+paq670)>=5 and totPA>=60
	then PAlevel=2; /*moderate PA level*/
	else PAlevel=3; /*low PA level*/
run; 

I got the following result and it seems that most of the calculations didn't go through. 

I got these log results. I am quite confused as to what happened. I'd really appreciate any help or advice. Thank you!

[ballardw]

Any calculation that involves a missing value for a variable is likely to result in a missing value for the entire line. You can reduce that to some extent by using the SUM function instead of +.

x= sum( 1,2,.) =>3

x= 1+2+.  => missing

So instead of

totPA=(paq610*pad615*8)+(paq625*pad630*4)+(paq640*pad645*4)+(paq655*pad660*8)+(paq670*pad675*4);

try

totPA=sum ((paq610*pad615*8),(paq625*pad630*4),(paq640*pad645*4),(paq655*pad660*8),(paq670*pad675*4) );

And similar for all the other additions you have.

Please post LOG entries in a code box opened with the forum's {I} or "running man" icon. It is extremely hard to copy and paste from a picture and make comments of the text.

[abigailpuno]

Thank you so much! It worked! I just needed to be careful about my parentheses, too. Really appreciate your time and effort answering my question. 🙂 

PS. Will post on the code box for the LOG next time. 🙂 Thanks for reminding. 

[indnahc]

Hello! Was wondering if you were able to help me? I have used the same exact code for my NHANES thesis this year with a different year's data set and have edited totPA=sum (x*x), (x*x).. etc how you have advised, however, am still not getting observations for the high level of PA. The same issue here as above! What else should I revisit in the code? Parenthesis? Change all addition equations to include a "sum" statement?