topic Re: What is the difference between select when and if ,else if in sas datastep can any one help in SAS Programming

What is the difference between select when and if ,else if in sas datastep can any one help

sas_Forum — Mon, 12 Mar 2012 07:22:31 GMT

What is the difference between select when and if ,else if in sas datastep can any one help

Ksharp — Mon, 12 Mar 2012 08:46:36 GMT

In my eyes, there is no difference between them.

But I would use select when you have lots of conditions to judge, because it is look elegant and succinct.

Ksharp

What is the difference between select when and if ,else if in sas datastep can any one help

ballardw — Mon, 12 Mar 2012 14:48:10 GMT

I would say the major difference is that If , else if allows more use of compound comparisons that may miss all of the cases you need to consider.

As Ksharp says if I need to consider more than 2 or 3 values for a single variable Select is easier to understand and I believe is supposed to execute quicker as it branches differently instead of evaluating a whole series of If then else if ....

The OTHERWISE statement with SELECT also serves as a better catch-all than a last "else" because different nesting in a series may not be as obvious that none of the criteria had been met.

I think the most cases I have dealt with in a single select when is around 194. I am not sure if you could even nest if then else that deep.

Re: What is the difference between select when and if ,else if in sas datastep can any one help

AjayKant — Fri, 17 Jan 2014 14:24:44 GMT

Just the way you use both work in similar phase and no need to understand difference because it give you same result .

as per your comfort you can either choose if then else or select when statement ;

I tried it on same dataset and find out the difference is how much they are used memory .

Dataset of 15000 observation and 20 variables is used to analyse .

Codes processed using IF

data if ;

set raw ;

if Region='Central' then do ;

code=1;

end ;

if Region='East' then do ;

code=2;

end ;

if Region='Wast' then do ;

code=3;

end ;

else code=0 ;

run ;

*----------------------------------------*

NOTE: There were 15000 observations read from the data set WORK.RAW.

NOTE: The data set WORK.IF has 15000 observations and 18 variables.

NOTE: DATA statement used (Total process time):

other is using select when

data when ;

set raw ;

select (Region);

when(central)do ;

code=1 ;

end ;

when(East)do ;

code=2 ;

end ;

when(West)do ;

code=3 ;

end ;

otherwise code=0 ;

end ;

run ;

----------------------------------------------

NOTE: There were 15000 observations read from the data set WORK.RAW.

NOTE: The data set WORK.WHEN has 15000 observations and 21 variables.

NOTE: DATA statement used (Total process time):

Timing used for processing IF

real time 0.03 seconds

user cpu time 0.01 seconds

system cpu time 0.01 seconds

memory 362.75k

OS Memory 6584.00k

Timestamp 01/17/2014 07:48:49 PM

Timing used for processing select when ;

real time 0.09 seconds

user cpu time 0.01 seconds

system cpu time 0.09 seconds

memory 367.62k

OS Memory 6584.00k

Timestamp 01/17/2014 07:51:27 PM

You find a bit difference in real time and cpu time ..

here is start using the way if data will increase to millions which SAS system actual have to work .

the difference can me measured easily .

I hope it will help you understand .

Re: What is the difference between select when and if ,else if in sas datastep can any one help

ballardw — Fri, 17 Jan 2014 14:29:23 GMT

Try the time difference coding

if Region='Central' then

Else if Region='West' then

else if Region='East' then

else

Re: What is the difference between select when and if ,else if in sas datastep can any one help

CTorres — Fri, 17 Jan 2014 14:53:47 GMT

You can simplify the select statement eliminating the do-end blocks innecesary in this case:

data when ;

set raw ;

select (Region);

when('Central') code=1 ;

when('East') code=2 ;

when('West') code=3 ;

otherwise code=0 ;

end ;

run ;

Re: What is the difference between select when and if ,else if in sas datastep can any one help

AjayKant — Fri, 17 Jan 2014 15:12:42 GMT

Can you explain what is time difference in content of this....

Re: What is the difference between select when and if ,else if in sas datastep can any one help

AjayKant — Fri, 17 Jan 2014 15:20:45 GMT

Thanks and its reduce the slight tie as well but yes in terms of performance if function works well .

The stats i get after re-edit the codes .

NOTE: There were 15000 observations read from the data set WORK.RAW.

NOTE: The data set WORK.IF has 15000 observations and 18 variables.

NOTE: DATA statement used (Total process time):

real time 0.03 seconds

user cpu time 0.00 seconds

system cpu time 0.01 seconds

memory 363.84k

OS Memory 6584.00k

Timestamp 01/17/2014 08:47:50 PM

NOTE: There were 15000 observations read from the data set WORK.RAW.

NOTE: The data set WORK.WHEN has 15000 observations and 21 variables.

NOTE: DATA statement used (Total process time):

real time 0.12 seconds

user cpu time 0.03 seconds

system cpu time 0.09 seconds

memory 365.62k

OS Memory 6584.00k

Timestamp 01/17/2014 08:47:50 PM

after re-editing the function works great but a major in there real time and CPU time and this is the only difference I found .