sas data step

What: The SAS data step is a very powerful way of reading and writing data. But looking at syntax, it is not obvious that it is a looping structure because there is no explicit looping syntax. It automatically reads through data sets in a circular manor. It's this circularity that gives SAS the ability to read and write data in a way that other database programs can't.

Writer: LucretiaGermanica

LCC:

Where: Reference Link Has Evaporated

Date: Mar 23 2011 3:11 AM

What: Visually and logically, the SAS data step is read vertically, from the top to the bottom. But the vertical syntax is processing something, the PDV, that could be though of as being a horizontal row of variables. What is this like? A vertical process conjoined to a horizontal process? How about the cargo list of a freight train with 10 cars. The cargo list if a vertical sequence of car numbers and their contents. When you go to look at the train, it is a define horizontal entity with each entity having a specific place in the train and with each entity having specific contents.

Writer: Lucretia

LCC:

Where: Reference Link Has Evaporated

Date: Apr 11 2013 11:57 AM

What: "Here is an analogy. DATA step processing is a bit like voting. When you arrive at your polling place, you stand in line behind other people who have come to vote. When you reach the front of the line you are asked standard questions: "What is your name? Where do you live?" Then you sign your name, and you cast your vote. In this analogy, the people are observations, and the voting process is the DATA step. People vote one at a time (or observation by observation). Each voter's choices are secret, and peeking at your neighbor's ballot is definitely frowned upon. In addition, each person completes each step of the process in the same order (line by line). You cannot cast your vote before you give your name and address. Everything must be done in the proper order." From page 9.

Writer: Susan J. Slaughter

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Where:

Date: Apr 10 2013 5:28 PM

What: The SAS data step processes a series of observations 1 at a time. This is somewhat like a line of travelers waiting in the customs line after arriving at an airport. The data step is like the inspection process and the statements in the data step are like the custom officer's questions. They can ask many questions: Who are you? How long are staying? Citizen or not? Who are you going to visit? Who did you visit? Do you have anything to declare? And so on. Depending on the answers, the travel is allowed to pass through,ie be output to the country or told they can't enter, not entered into the new data set. Something like: if passenger="terrorist" then delete;

Writer: Lucretia

LCC:

Where: Reference Link Has Evaporated

Date: Apr 10 2013 6:24 PM