SAS code to find the estimate of a comparison group

ak2011 — Fri, 14 Aug 2020 19:29:55 GMT

Hello,

I would appreciate if someone could help me with the SAS code in logistic regression to find the estimate log odds/odds ratio of a comparison/reference group (refgroup) above. I have the same refgroup for the 2 agents(a1exp and a2exp).

I used a similar approach to the solution to my previous question that I posted on the forum and which was answered by someone. I am posting another question quite different from what I posted before.

Unexposed = 0, exposure levels: 1= high and 2=low.

Thanks in advance.

ak.

Main focus: Refgroup column; how to compute the ORs using logistic regression.

Reference group(refgroup) is composed of subjects (ids) not exposed to either of the agents(a1exp or a2exp). 2 ca cases (cases) and 6 pop cont(controls) met the criterion.

Please find below my code and log. Results are attached(Table 5: Exposure levels).

data expinfo;
input id$ 1-4  a1exp 6-7 a1exp_level$ 8-17  a1exp_cat 19-20  
a2exp 26-27 a2exp_level$ 28-32 a2exp_cat 39-40  lung$ 48-55;
datalines;
os1  0 unexposed  0      1 high       1        ca case  
os2  1 low        2      0 unexposed  0        ca case  
os3  0 unexposed  0      0 unexposed  0        pop cont
os4  1 high       1      1 low        2        pop cont 
os5  0 unexposed  0	 0 unexposed  0        pop cont
os6  1 low        2      0 unexposed  0	       ca case
os7  1 low        2      1 high       1        ca case  
os8  0 unexposed  0      0 unexposed  0        ca case  
os9  0 unexposed  0      0 unexposed  0        pop cont
os10 1 high       1      1 low        2        pop cont 
os11 0 unexposed  0	 0 unexposed  0        ca case 
os12 1 low        2      0 unexposed  0	       ca case
os13 1 high       1      1 low        2        ca case  
os14 0 unexposed  0      0 unexposed  0        pop cont  
os15 0 unexposed  0      0 unexposed  0        pop cont
os16 1 high       1      1 low        2        pop cont 
os17 0 unexposed  0	 1 high       1        pop cont 
os18 0 unexposed  0      0 unexposed  0	       pop cont
;
run;

/*proc print data=expinfo;

Title 'Table 1: Exposure of ids to 2 agents';*/

  /*Step 1: Finding number of cases and controls unexposed to agents(a1,a2,a3 and a4)*/  
proc freq data=expinfo(where=(sum(a1exp,a2exp)=0));
     tables lung;
title 'Table 1:Subjects unexposed to either of the 2 agents';
run;

 
 
/*Step 2:Using subjects unexposed to any of agents as a ref. group*/

proc sql;
create table t as 
  select
    id, a1exp, a2exp,lung,
    sum(a1exp,a2exp)=0 as refgroup
     from expinfo
     ;
     quit;
     
proc print data=t; 
   title 'Table 2a: original variables and ref group';
   run;
   
    proc freq data=t;
    tables lung* refgroup;
    title 'Table 2b: freq of ca case and pop cont for ref group';
    run;
proc freq data=expinfo;
    tables lung* a1exp_level lung*a1exp_cat  
     lung* a2exp_level lung*a2exp_cat   ;
    title 'Table 3: freq of ca case and pop cont for vs lung';
    run;
 
data logtest; set t;
if lung in ('ca case','pop cont');
run;

 proc logistic data=logtest;
model lung(event='ca case') =refgroup;  
Title 'Table 4: Estimates for ref. group';
run;

1 OPTIONS NONOTES NOSTIMER NOSOURCE NOSYNTAXCHECK;

73 data expinfo;

74 input id$ 1-4 a1exp 6-7 a1exp_level$ 8-17 a1exp_cat 19-20

75 a2exp 26-27 a2exp_level$ 28-32 a2exp_cat 39-40 lung$ 48-55;

76 datalines;

NOTE: The data set WORK.EXPINFO has 18 observations and 8 variables.

NOTE: DATA statement used (Total process time):

real time 0.01 seconds

cpu time 0.02 seconds

95 ;

96 run;

98 /*proc print data=expinfo;

100 Title 'Table 1: Exposure of ids to 2 agents';*/

101

102 /*Step 1: Finding number of cases and controls unexposed to agents(a1,a2,a3 and a4)*/

103 proc freq data=expinfo(where=(sum(a1exp,a2exp)=0));

104 tables lung;

105 title 'Table 1:Subjects unexposed to either of the 2 agents';

106 run;

NOTE: There were 8 observations read from the data set WORK.EXPINFO.

WHERE SUM(a1exp, a2exp)=0;

NOTE: PROCEDURE FREQ used (Total process time):

real time 0.20 seconds

cpu time 0.20 seconds

107

108

109

110 /*Step 2:Using subjects unexposed to any of agents as a ref. group*/

111

112 proc sql;

113 create table t as

114 select

115 id, a1exp, a2exp,lung,

116 sum(a1exp,a2exp)=0 as refgroup

117 from expinfo

118 ;

NOTE: Table WORK.T created, with 18 rows and 5 columns.

119 quit;

NOTE: PROCEDURE SQL used (Total process time):

real time 0.01 seconds

cpu time 0.01 seconds

120

121 proc print data=t;

122 title 'Table 2a: original variables and ref group';

123 run;

NOTE: There were 18 observations read from the data set WORK.T.

NOTE: PROCEDURE PRINT used (Total process time):

real time 0.22 seconds

cpu time 0.22 seconds

124

125 proc freq data=t;

126 tables lung* refgroup;

127 title 'Table 2b: freq of ca case and pop cont for ref group';

128 run;

NOTE: There were 18 observations read from the data set WORK.T.

NOTE: PROCEDURE FREQ used (Total process time):

real time 0.16 seconds

cpu time 0.15 seconds

129 proc freq data=expinfo;

130 tables lung* a1exp_level lung*a1exp_cat

131 lung* a2exp_level lung*a2exp_cat ;

132 title 'Table 3: freq of ca case and pop cont for vs lung';

133 run;

NOTE: There were 18 observations read from the data set WORK.EXPINFO.

NOTE: PROCEDURE FREQ used (Total process time):

real time 0.52 seconds

cpu time 0.52 seconds

134

135 data logtest; set t;

136 if lung in ('ca case','pop cont');

137 run;

NOTE: There were 18 observations read from the data set WORK.T.

NOTE: The data set WORK.LOGTEST has 18 observations and 5 variables.

NOTE: DATA statement used (Total process time):

real time 0.01 seconds

cpu time 0.02 seconds

138

139 proc logistic data=logtest;

140 model lung(event='ca case') =refgroup;

141 Title 'Table 4: Estimates for ref. group';

142 run;

NOTE: PROC LOGISTIC is modeling the probability that lung='ca case'.

NOTE: Convergence criterion (GCONV=1E-8) satisfied.

NOTE: There were 18 observations read from the data set WORK.LOGTEST.

NOTE: PROCEDURE LOGISTIC used (Total process time):

real time 0.44 seconds

cpu time 0.40 seconds

143

144

145 OPTIONS NONOTES NOSTIMER NOSOURCE NOSYNTAXCHECK;

157

Re: SAS code to find the estimate of a comparison group

Ksharp — Sat, 15 Aug 2020 12:13:34 GMT

Better post it at Stat Forum. @StatDave @Rick_SAS could give you a hand.

Re: SAS code to find the estimate of a comparison group

Rick_SAS — Sat, 15 Aug 2020 13:14:28 GMT

I think the OP cross-posted this message. This entry in the Statistical Community looks the same:

https://communities.sas.com/t5/Statistical-Procedures/Creating-a-reference-group-from-unexposed-subjects-and-finding/m-p/676852#M32443

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SAS code to find the estimate of a comparison group

Re: SAS code to find the estimate of a comparison group

Re: SAS code to find the estimate of a comparison group