format and informat?

[ybz12003]

Hello:

I have the following codes by created someone else.   Could anyone let me know why use informat and format together?  Thanks.

data test;
	set test;
	array aa &numrvar;
 	do over aa;
  	aa=datepart(aa);
end;
	informat &NUMRVAR MMDDYY10.; 
	format &NUMRVAR MMDDYY10.; 
run;

[Kurt_Bremser]

Informats are not needed when no external data is read.

[Reeza]

And DO OVER has been deprecated. 

When you see code like this, one of two things likely happened:

1. The original author didn't understand informats

2. At one point the data was being read from a text file and then the process change and code was updated, but this was left in. 

[Tom]

An INFORMAT is instructions for converting text to values. A FORMAT is instructions for converting values to text.

You need the FORMAT statement so that the dates will display in a human readable way.  You do not need to attach the informats for this program since you are not using them anywhere.  But it doesn't hurt.  And since you are converting from DATETIME to DATE values you probably do want to at least remove whatever INFORMATs were previously attached to those variables.

informat &NUMRVAR ; 

The informats might be useful later if you want to add observations using FSEDIT for example.

Or if you want to use the dataset as a template for reading some raw data.  You need an informat SAS to read values like '10/17/2018' as a number and not just a string.

data new;
  if 0 then set test;
  infile 'newdata.csv' dsd truncover ;
  input (_all_) (+0);
run;

[ybz12003]

Based on your feedback, I found out the original code is like this.   Does this means that library RSV is outside source, therefore, informat is used for external file?

data ARI18_&tdate.;
	set RSV."18ARI"n;
	array aa &numrvar;
 	do over aa;
  	aa=datepart(aa);
end;
	informat &NUMRVAR MMDDYY10.; 
	format &NUMRVAR MMDDYY10.; 
run;

[Tom · Accepted solution]

Yes. 

A number of DBMS systems do not have a concept of a date (number of days) and just have a general datetime (or timestamp) data type.  So people store dates with either a constant time part (like midnight) or perhaps the system supports some metadata that tells it how precise the timestamp value is.

So that SAS code will convert the values form number of seconds to number of days and adjust the formats/informats to those more appropriate for a date value.

[ybz12003]

Thank you so much for all of your valuable information.