Cant resolve a script

[tradermartin]

Hello, I would like to ask you for help. I am not a SAS user but now I try to solve one script from a book. Please find attached print screen. Could you please explain what should occur after a run the script? Unfortunately I don't know SAS syntax and the answer is urgent for me.

What exactly means the part "set data.deve (in = a) data.deve (in = b);". What the author tried to do before the logistic regression?? What are "a" and "b"? They are in the previous imported data or they are now generated?

Thank you very much!

 

[Con-Tester]

The “a” and “b” are indicators that are used to decide whether the record currently being processed in the “data” step comes from the first dataset or the second one. They are numerical values and will have the value 0 or 1—0 if the current record is not in the dataset to which the indicator belongs, or 1 if it is. So, a record from the first dataset has a = 1 and b = 0, while a record from the second one has a = 0 and b = 1.

Normally, the two (or more) datasets would be different ones, though with the same columns (but again, not always). That is, the usual syntax would be something like “set s1 (in = a) s2 (in = b) s3 (in = c) …;” and therefore I suspect that “set data.deve (in = a) data.deve (in = b);” may be a typo.

If it is not a typo, then the output dataset (“data deve;” in the “work” library—the screenshot is too fuzzy to read clearly) will contain double the number of records in “data.deve” except that the duplicate records will have different values for the “y2” and “wt” variables.

The subsequent “proc logistic” step then fits a logistic model to the data.

 

[tradermartin]

Thank you very much. But still I have problem to understand the whole process...Please, check my hypothesis below.

First of all, "If it is not a typo, then the output dataset (“data deve;” in the “work” library—the screenshot is too fuzzy to read clearly) will contain double the number of records in “data.deve” except that the duplicate records will have different values for the “y2” and “wt” variables."

yes, you are right, the result should be to duplicate observations but with different y2 and its respective weight

But, how does the procedure "set data" work?

for simplified purpose lets imagine that this is my raw data (result of import procedure):

y var1 var2
0.2 25 1
0 20 0.88
0.99 50 1.55

How will my data look like after “set s1 (in = a) s2 (in = b) s3 (in = c) …;” ?

y var1 var2 s1 y2 wt
0.2 25 1 a 1 0.2
0 20 0.88 a 1 0
0.99 50 1.55 a 1 0.99
0.2 25 1 a 0 0.8
0 20 0.88 a 0 1
0.99 50 1.55 a 0 0.01

This will be my results?

If yes, how can the procedure differentiate to which rows assign the "a" and to which rows assign the "b"?

please, try to explain me the procedure of "set data" because it is very important for me how it works...Lets imagine that I need to adjust my data in Excel in the same way how it did the SAS in the procedure in the print screen. Thank you in advance!

 

[Con-Tester]

I used “set s1 (in = a) s2 (in = b) s3 (in = c) …;” as a general example to show the syntax of the “in” indicator variables, i.e. “a”, “b”, “c”, etc. The “s1”, “s2”, “s3”, etc. are dataset names, not variable names. The “data” step runs through each dataset listed in the “set” clause in the order in which they are listed.

Using your example for the dataset “data.deve” (see attached Fig1.png), after running the “data” step (the code from “data deve;” to the first “run;” statement) will output a dataset called “deve” that lives in the SAS session’s “work” library and has the contents as shown in the attached Fig2.png.

If you still don’t understand, run the code in SAS yourself.

 

[tradermartin]

Thank you very much. Your demonstration using tables helped me

BTW: i tried to run the script (after replacing name of database and attributes), but it doesn't work. It gave me a error message that my table may be not complete or something... Have you tried to run it?? (maybe it is truly a type as you mentioned but it is from a research paper)

 

[Con-Tester]

I did run it for the example data you provided, after generating a “deve” dataset with three records, as per the example.

You need to copy the contents of the SAS log and post it here (or provide a nice and legible screen shot thereof) because your description is insufficient. Maybe a library is not assigned or a dataset is missing or there’s a syntax error.

 

[tradermartin]

I will try it again and let you know...

 

[noetsi]

Printing the log would help a lot.