tal <talila.ar@GMAIL.COM> wrote
>I'm not sure- but i don't think the sampling is stratified. i have ,
>lets say:20 variables- "is XX important to you?" for each quest the
>1- important 2- not important 3-no answer.
>(When i use the class statement- 3 dummy variables are created, but
>I'm only interested in the first two- the third one is created
>automatically- but i don't need it- and that's where I have a
>problem) As i said , for each observation i want to count the number
>of missing values in the questionnaire- and take it as explanatory
>variable- but since a dummy variable is created for each var1-var20
>the number of missing values is a linear combination of these.
> Does anybody know how to create only the 2 dummy variables that i
>need in proc logistic, and drop the third one?
If your IV has 3 levels, then LOGISTIC will create 2 dummy variables;, by default SAS uses EFFECT coding, and dummy (or reference) coding, is often better, but I don't think that explains your problem
So, could you show your code?
length IV $4;
input iv $ dv $ weight;
Imp yes 100
NotI yes 200
NA yes 50
Imp no 50
NotI no 100
NA no 50
proc logistic data = today;
class iv (param = ref);
model dv = iv;
creates two dummy variables
Peter L. Flom, PhD
www DOT peterflom DOT com