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03-18-2013 09:40 AM

**Hi all, below is simple example of proc forecast:**

**data** pred;

a=**1**;b=**1**;output;

a=**1**;b=**2**;output;

a=**1**;b=**3**;output;

a=**1**;b=**4**;output;

a=**1**;b=**5**;output;

a=**2**;b=**2**;output;

a=**2**;b=**4**;output;

a=**2**;b=**6**;output;

a=**2**;b=**8**;output;

a=**2**;b=**10**;output;

**run**;

**proc** **forecast** data=pred lead=**1** out=next(keep=a b);

by a;

**run**;

Results is:

/* a b

1 6

2 12

*/

**But** if input data set has not enough records for analyze,proc forecast fails with error:Too few observations to fit model. At least 5 observations are required. Check your data.

**data** pred;

a=**1**;b=**1**;output;

a=**1**;b=**2**;output;

a=**1**;b=**3**;output;

a=**1**;b=**4**;output;

a=**1**;b=**5**;output;

a=**2**;b=**2**;output;

a=**2**;b=**4**;output;

**run**;

**proc** **forecast** data=pred lead=**1** out=next(keep=a b);

by a;

**run**;

/* Results:

1 6

ERROR: Too few observations to fit model. At least 5 observations are required. Check your data.

*/

So is it possible rid off(ommit) this error message? I mean - if for small "by group" isn't enough rows for forecasting- ommit this row(without error message) and continue process next by groups.

I suppose 5 records can be also not enough in some cases.

Thanks!

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03-18-2013 10:15 AM

I believe it is hard to turn off error message completely (SAS would wonder why), "Warn" can sometimes be suppressed. In your case, this kind of error will NOT stop SAS from processing incoming data, so it won't "fail", per se. One way to limit the error message is to set:

MAXERRORS=

Again, you can't set it to '0', the minimum number you can set is '1'.

Haikuo

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03-18-2013 10:34 AM

Hello Haikuo,

Actually I tried this option before, and it didn't helped:

**data** pred;

a=**1**;b=**1**;output;

a=**1**;b=**2**;output;

a=**1**;b=**3**;output;

a=**1**;b=**4**;output;

a=**1**;b=**5**;output;

a=**2**;b=**2**;output;

a=**2**;b=**4**;output;

**run**;

**proc** **forecast** data=pred lead=**1** out=next(keep=a b) MAXERRORS=**10**;

by a;

**run**;

If you'll try this code error will still occurs...

May be there some global option, smth. like noerrorstop in proc sql?

I should somehow eliminate these groups of data that are not ok for proc forecast...

Thanks!

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03-18-2013 10:58 AM

Like I said, MAXERRORS= will NOT eliminate your error message, but it will put a leash on it. Please look at the following example, try with/without commented option:

data pred;

do b=1 to 3;

a=1;output;

end;

do b=2 by 2 to 6;

a=2;output;

end;

do b=3 by 3 to 21;

a=3;output;

end;

run;

proc forecast data=pred lead=1 out=next(keep=a b) /*MAXERRORS=1*/ start=6;

by a;

run;

With " MAXERRORS=1 " in effect, you only get 1 error message; without, you get as many as it is supposed to be, here you will get 2. Bottom line, you will obtain your outcome table with those successfully processed data.

HTH,

Haikuo

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03-18-2013 11:09 AM

Hi Again,

Thanks, it's clear.

Anyway it will not fix the problem, maybe I'll just eliminate all groups that have less then 5 records and will hope that it(5 and more recs in group) will be enough for proc forecast

Thanks!

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03-18-2013 11:21 AM

Hi again,

I've just checked - and proc forecast really needs different min amount of input records for make forecasting, obviously depends on data...

Not nice but if there are no another solutions I think I should leave this macro code as it is and ignore the errors...

Anyway thanks!

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03-18-2013 11:07 AM

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03-18-2013 11:13 AM

Hi again,

Yes yes, initially I also thougt about this , but as I remember I saw cases were even 6 records were not enough for proc forecast, I'm not sure about this , I use this proc just a few hours, so I will chack it one more time...

Thansk!

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03-18-2013 03:38 PM

Hello -

You may try the following:

data pred;

a=1;b=1;output;

a=1;b=2;output;

a=1;b=3;output;

a=1;b=4;output;

a=1;b=5;output;

a=2;b=2;output;

a=2;b=4;output;

run;

proc esm data=pred lead=1 out=next;

forecast b / method=linear;

by a;

run;

A couple of notes:

- ESM runs exponential smoothing models with optimized parameters. Given your example a linear (Holt) exponential smoothing model seems to make sense, but the question remains if this is always the case (is a linear ESM always appropriate?).
- The FORECAST procedure will apply the STEPAR Algorithm by default - its data requirements are described here: http://support.sas.com/documentation/cdl/en/etsug/63939/HTML/default/viewer.htm#etsug_forecast_sect0...
- If you have only a few observations (like 2 in your example) available any forecasting technique becomes questionable of course. Maybe you are more concerned about fitting a linear regression line to your data and then extrapolate it to include new observations? In this case you are better off using the REG procedure of course. The question is if your data is autocorrelated.

Thanks,

Udo

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03-19-2013 03:31 AM

Hi Udo,

I believe that ESM procedures can be solution in my case, but my SAS version SAS 9.1.3 and due my licence I haven't ESM procedure...

But all your three notes make sence, Yestarday I used forecast procedure only first time and was very pleasent surprise with forecast values that it provides, but you are right, first of all I should try add as many observation to input algorithm as possible, then I should choose corrrect algorithm etc.

Thanks!