create new variable using input and format

[stataq]

Hello,

I have a silly question. I saw people use proc format and then build new variable with it.

I saw some used 

Region = put(parkcode, $reglbl.);

 but some used 

Region=put(parkcode, ??  reglbl.)

what are the difference. I am very confused on '??' part. Could anyone guide me on this?

Thanks.

[Astounding · Accepted solution]

?? can be used with the INPUT function, not the PUT function.  Consider these variations:

n1 = input('ABC', 3.);
n2 = input('ABC', ?? 3.);

The first statement would give you a message about invalid data being read since the 3. informat looks to create a numeric value.  And "ABC" can't be read as numeric.

In a way, the second statement gives the same outcome in that n1 will equal n2.  However, the ?? suppresses any messages in the log about invalid data.

[stataq]

Thanks. So "??" is for cleaner log file? when do we need to use "??" instead? 

[Tom]

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@stataq wrote:

Thanks. So "??" is for cleaner log file? when do we need to use "??" instead? 

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You don't NEED to use it. 

You might WANT to use it when:

• You know that some of the original values might not be valid for the INFORMAT being used.
• You do not need to distinguish between those original values.  They will be mapped to missing.
• You do not want the SAS log to display the invalid values.