FIRSTOBS= System Option
Specifies the observation number or external file
record that SAS processes first.
| Valid in: |
Configuration file, SAS invocation, OPTIONS statement, SAS
System Options window
|
| Category: |
Files: SAS Files |
| PROC OPTIONS GROUP= |
SASFILES |
| Interaction: |
When you specify the FIRSTOBS= option and EXTENDOBSCOUNTER=YES
is set either as a data set option or as a LIBNAME option, data sets
that have 2G–1 observations or more might perform better in
a 32-bit environment. For more information, see Extending the Observation Count in a SAS Data File in SAS Language Reference: Concepts. |
| Note: |
This option can be restricted by a site administrator. For more information,
see Restricted Options. |
Syntax
Syntax Description
- n | nK | nM | nG | nT
-
specifies the number
of the first observation or external file record to process, with n being an integer. Using one of the letter notations
results in multiplying the integer by a specific value. That is, specifying
K (kilo) multiplies the integer by 1,024; M (mega) multiplies by 1,048,576
; G (giga) multiplies by 1,073,741,824; or T (tera) multiplies by
1,099,511,627,776. For example, a value of 8 specifies the eighth observations or records, and a value of 3m specifies observation or record 3,145,728.
- hexX
-
specifies the number
of the first observation or the external file record to process as
a hexadecimal value. You must specify the value beginning with a number
(0–9), followed by an X. For example, the value 2dx specifies the 45th observation.
- MIN
-
sets the number of
the first observation or external file record to process to 1. This
is the default.
- MAX
-
sets the number of
the first observation to process to the maximum number of observations
in the data sets or records in the external file, up to the largest
eight-byte, signed integer, which is 263-1, or approximately 9.2 quintillion observations.
Details
The FIRSTOBS= system
option is valid for all steps for the duration of your current SAS
session or until you change the setting. To affect any single SAS
data set, use the FIRSTOBS= data set option.
Comparisons
-
You can override the FIRSTOBS=
system option by using the FIRSTOBS= data set option and by using
the FIRSTOBS= option as a part of the INFILE statement.
-
While the FIRSTOBS= system option
specifies a starting point for processing, the OBS= system option
specifies an ending point. The two options are often used together
to define a range of observations or records to be processed.
Example
If you specify FIRSTOBS=50,
SAS processes the 50th observation of the data set first.
This option applies
to every input data set that is used in a program or a SAS process.
In this example, SAS begins reading at the 11th observation in the
data sets OLD, A, and B:
options firstobs=11;
data a;
set old; /* 100 observations */
run;
data b;
set a;
run;
data c;
set b;
run;
Data set OLD has 100
observations, data set A has 90, B has 80, and C has 70. To avoid
decreasing the number of observations in successive data sets, use
the FIRSTOBS= data set option in the SET statement. You can also reset
FIRSTOBS=1 between a DATA step and a PROC step.