Guide SAS VIYA

SAS Viya Tutorial: Import a Headerless Text File and Rename Columns Dynamically

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Veröffentlicht am : 23/05/2022

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Michael

While dynamically renaming variables via PROC DATASETS is highly efficient since it updates metadata without rewriting the underlying data, relying on PROC IMPORT can sometimes lead to costly data type misinterpretations. For robust, production-grade data pipelines in SAS Viya, prioritize writing a custom DATA step with an INFILE statement from the start to guarantee absolute control over formats, lengths, and memory allocation.

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When importing flat files (CSV, TXT) into SAS^© Viya^™ via PROC IMPORT, a common scenario poses a problem: the data file does not contain a header row, and the column names are provided separately (for example, in a Word or Excel document).

By default, if you use the GETNAMES=NO option, SAS^© generates generic names (VAR1, VAR2, VAR3...).

How can you efficiently apply your own column names without manually renaming each variable, especially if the file contains dozens of them? Here are two approaches: the quick method for a few variables, and complete automation for large files.

1. The Standard Method (PROC IMPORT + RENAME)

If you have few columns, the simplest solution is to import the file as is, then rename the variables afterward.

Step 1: Raw Import

Use the GETNAMES=NO option to tell SAS^© that the first line already contains data.

1	FILENAME LOC DISK '/workspace/workbench/myorg/data/home/olddatatoimport.txt';
2
3	PROC IMPORT DATAFILE=LOC
4	DBMS=DLM
5	OUT=WORK.NEWDATA
6	REPLACE;
7	DELIMITER=','; /* ou '09'x pour tabulation */
8	GETNAMES=NO; /* Crucial : évite de perdre la 1ère ligne de données */
9	RUN;

Step 2: Manual Renaming

Use PROC DATASETS to modify the names without re-reading all the data (very fast even on large volumes).

1	PROC DATASETS library=WORK nolist;
2	modify NEWDATA;
3	rename
4	VAR1 = State
5	VAR2 = City
6	VAR3 = Population;
7	QUIT;

2. The Automated Method (Dynamic Renaming)

If you have 50 or 100 columns listed in an external document, the manual method is tedious and prone to errors. Here’s how to automate the process by dynamically generating the RENAME statement.

The Concept

Import the data file with generic names (VAR1, VAR2...).
Import the list of column names (copied from your Word/Excel document) into a SAS^© table.
Use a Data Step to build a macro variable containing the pair VAR1=NewName VAR2=AnotherName.
Apply this macro in PROC DATASETS.

The Complete Code

Phase A: Create the names table Copy your list of columns from Word and paste it into the code below:

1	/* Table contenant vos noms de colonnes dans l'ordre du fichier */
2	DATA column_names;
3	LENGTH new_name $32;
4	INPUT new_name;
5	DATALINES;
6	State
7	City
8	ZipCode
9	Population
10	Revenue
11	/* ... collez votre liste ici ... */
12	;
13	RUN;

Phase B: Generate the renaming script This code loops through the list of names and builds a character string of the type: VAR1=State VAR2=City ...

1	DATA _null_;
2	SET column_names END=last;
3
4	LENGTH rename_list $32000;
5	retain rename_list;
6
7	/* On concatène : "VAR" + numéro de ligne = "Nouveau Nom" */
8	/* cats('VAR', _n_) génère VAR1, VAR2, etc. basée sur le numéro de ligne */
9	rename_list = catx(' ', rename_list, catx('=', cats('VAR',_n_), new_name));
10
11	/* À la fin, on stocke tout dans une variable macro &PAIRES_RENAME */
12	IF last THEN call symputx('PAIRES_RENAME', rename_list);
13	RUN;
14
15	/* Vérification dans le journal */
16	%put &PAIRES_RENAME;

Phase C: Apply the change

1	/* Importation des données brutes */
2	PROC IMPORT datafile='/chemin/mon_fichier.txt' dbms=dlm out=work.raw_data replace;
3	getnames=no;
4	RUN;
5
6	/* Renommage éclair */
7	PROC DATASETS library=work nolist;
8	modify raw_data;
9	rename &PAIRES_RENAME;
10	QUIT;

Alternative: The DATA Step (Total Control)

If your file is complex (specific dates, particular numeric formats), PROC IMPORT can sometimes guess the data types incorrectly. In this case, the most robust method is to write a classic DATA step.

1	DATA work.newdata;
2	INFILE '/workspace/workbench/myorg/data/home/olddatatoimport.txt'
3	dsd /* Gère les délimiteurs et les valeurs manquantes */
4	dlm=',' /* Délimiteur */
5	truncover; /* Évite les erreurs si une ligne est trop courte */
6
7	/* Définissez vos noms et types ici */
8	INPUT
9	State :$2.
10	City :$50.
11	Population :best.
12	Revenue :comma10.;
13	RUN;

For a quick need: PROC IMPORT (GetNames=No) + PROC DATASETS.

For a large number of columns: Automation via Macro Variable.

For precise control over types: DATA Step with INPUT.

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