How to Use INTNX Function in SAS (With Examples)

You can use the INTNX function in SAS to increment a date by a specific interval such as a day, week, month, etc.

This function uses the following basic syntax:

INTNX(interval, start_date, increment)

where:

interval: The interval to add to date (day, week, month, year, etc.)
start_date: Variable that contains start dates
increment: The number of intervals to add

To subtract an interval, supply a negative number to the increment argument.

The following examples show some common ways to use the INTNX function in practice with the following dataset in SAS:

/*create dataset*/
data original_data;
    format date date9.;
    input date :date9. sales;
    datalines;
01JAN2022 50
01FEB2022 34
14MAR2022 26
01MAY2022 22
24AUG2022 27
28OCT2022 48
14NOV2022 97
04DEC2022 88
;
run;

/*view dataset*/
proc print data=original_data;

Example 1: Use INTNX to Add Days to Date

We can use the INTNX function to create a new column called plus5days that adds five days to each date in the date column:

/*create new dataset with column that adds 5 days to date*/
data new_data;
    set original_data;
    plus5days=intnx('day', date, 5);
    format plus5days date9.;
run;

/*view dataset*/
proc print data=new_data;

Notice that the new column called plus5days contains the values in the date column with fives days added to them.

Example 2: Use INTNX to Subtract Days from Date

You can also subtract days by simply using a negative value in the INTNX function.

For example, we can use the following code to subtract five days from each value in the date column:

/*create new dataset with column that subtracts 5 days from date*/
data new_data;
    set original_data;
    minus5days=intnx('day', date, -5);
    format minusdays date9.;
run;

/*view dataset*/
proc print data=new_data;

Notice that the new column called minus5days contains the values in the date column with fives days subtracted from them.

Example 3: Use INTNX to Find First Day of Month

We can use the INTNX function to create a new column called firstmonth that contains the first day of the month for each date in the date column:

/*create new dataset with column that contains first day of the month*/
data new_data;
    set original_data;
    firstmonth=intnx('month', date, 0);
    format firstmonth date9.;
run;

/*view dataset*/
proc print data=new_data;

Notice that the new column called firstmonth contains the first day of the month for each date in the date column.

Example 4: Use INTNX to Find First Day of Year

We can also use the INTNX function to create a new column called firstyear that contains the first day of the year for each date in the date column:

/*create new dataset with column that contains first day of the year*/
data new_data;
    set original_data;
    firstyear=intnx('year', date, 0);
    format firstyear date9.;
run;

/*view dataset*/
proc print data=new_data;