Got it. Makes more sense now. Thank you so much! ... View more

Thank you for the response. I think I'm beginning to understand better. So, just to make sure, let me try to explain.   I will use the code that you gave previously, except I won't drop the variable "year" from the do loop:     data banks; input name : $ 13. rate; datalines; FirstCapital 0.0718 DirectBank 0.0721 VirtualDirect 0.0728 fourthbank 0.05 ; run; data newbank; do year=1 to 3; set banks; output; end; run; Output:       Obs year name rate 1 1 FirstCapital 0.0718 2 2 DirectBank 0.0721 3 3 VirtualDirect 0.0728 4 1 fourthbank 0.0500 Here's my explanation of what is going on (also I have a question in red font color😞     1. First iteration of data step First iteration of do loop (year = 1) First observation of the dataset is read and output is given (code: set banks; output;) Second iteration of do loop (year = 2) Second observation of the dataset is read and output is given (code: set banks; output;) Third iteration of do loop (year = 3) Third observation of the dataset is read and output is given (code: set banks; output;) End of do loop and end of first iteration of data step 2. Second iteration of data step First iteration of do loop (year = 1) Fourth observation of the dataset is read and output is given (code: set banks; output;) How does SAS know to read the fourth observation of the input dataset here? Is there some sort of a pointer? End of file reached. EOF = 1 Second iteration of do loop (year = 2) Terminate data step because EOF  = 1. No output is given Please correct/clarify. ... View more

Thank you for the exercise. This is a good point and it helps me to understand what is going on behind the scenes when combining datasets. ... View more

I see. Thank you for this as this is a good exercise. My explanation is that the do loop will go from year = 1 to year = 3 by 1s. In addition to this, there's the implicit loop of the data step. This will read the input dataset one observation at a time until the end of the dataset. Since there are four observations, the output dataset will also have four observations even though the do loop only goes from 1 to 3. So, even though the set statement is inside a do loop, the set statement will be controlled by the implicit data step loop. That is, all the observations in the set statement will only be read once.   Please correct/clarify my understanding as you see fit. ... View more

Thank you for the reply. This is very helpful.   I would accept this as a solution as well but I'm not sure how to have multiple answers as solutions. ... View more

Thank you for the thorough response. It is very helpful. From all your examples, I am beginning to understand that there are two different loops going on in #1. That is, first, there's one loop for the do loop (year = 1 to year = 3). And then, second, there's the implicit loop of the data step. This reads all the observations in the input dataset (from the set statement) independent of the do loop. Please correct/clarify if my understanding is wrong. Otherwise, this has been very helpful. Thanks again. ... View more

Ah got it. That was helpful. Thank you again!   I would accept this as a solution as well but I'm not sure how to have multiple answers as solutions. ... View more

Also, can you resend the pdf link? It doesn't seem to work for me. ... View more

I see. What about in the first code block? Don't I have the data set open three times as well since the set statement is inside a DO loop? ... View more

Awesome! Thank you! ... View more