How to Get Data into SAS
If you have an ascii file containing your data, you can easily read it
into a SAS dataset. SAS will read your data no matter how it looks in
the file, but in the simpliest case, data either be in columns or space
separated. For example, it could look like this:
1 2
1--------0---------0---- <= Column
Daffy Duck 5
Porky Pig 3
Road Runner 4
Hewey 3
This type of data format is called "column input format"; you tell SAS
how to read each variable by specifying the columns it occupies in
the file. Missing values are notated by no value in the specified
column.
Your data file could also look like this:
Daffy Duck 5
Porky Pig 3
Road Runner 4
Hewey . 3
This format is called "list input format"; SAS recognizes that a
space separates your variables. In list input format:
* Fields must be separated by at least one blank
* Fields must be in a specified order
* Missing values must be represented by a place holder such
as a period (.)
* Character values longer than 8 characters need to be
treated specially
* Data cannot be in special formats (eg dates)
If your data is in one of these two simple forms, it is very easy to
write a SAS program to read it in. The SAS statement 'input' allows you
to describe your data format to SAS. To read variables in list input
format, simply name the variables on the input line, adding a $ for
variables which are made up of characters instead of numbers. For
example, this input statement would read our sample data:
input first $ last $ age;
To read the same data in column input format, you need to specify the
columns each variable occupies:
input first $ 1-10 last $ 12-20 age 24;
To put it all together into a complete SAS step (A step is a series of
SAS statements), add lines resembling the following:
data <name>;
infile '<pathname>';
input <input specification>;
run;
Where
<pathname> is the UNIX pathname to your data file
<name> is an 8 character (or less) name for your dataset
internal to SAS. By default it will be a temporary
dataset.
<input specification> is the input line as above.
A specific example would look like this:
data tdata;
infile '/mit/joeuser/sasdata';
input first $ 1-10 last $ 11-20 age 22;
run;
If your data is not this simple, or you want further information,
consult the following SAS documentation:
SAS Language and Procedures, Usage Version 6, First Edition
chapters 2-4
SAS Language, Reference Version 6, First Edition
INFILE statement pgs 377-389
INPUT statement pgs 393-422
Both of these documents are available from the consultants in N42.
|
