The for..next control statement is a script iteration construct with a counter. The statements inside the loop enclosed by for and next will be executed for each value of the counter variable between specified low and high limits.
Syntax:
For counter = expr1 to expr2 [ step expr3 ]
[statements]
[exit for [ ( when | unless ) condition ]
[statements]
Next [counter]
The expressions expr1, expr2 and expr3 are only evaluated the first time the loop is entered. The value of the counter variable may be changed by statements inside the loop, but this is not good programming practice.
If an exit for clause is encountered inside the loop, the execution of the script will be transferred to the first statement after the next clause denoting the end of the loop. An exit for clause can be made conditional by the optional use of a when or unless suffix.
Arguments:
| Argument | Description |
|---|---|
| counter | A variable name. If counter is specified after next it must be the same variable name as the one found after the corresponding for. |
| expr1 | An expression which determines the first value of the counter variable for which the loop should be executed. |
| expr2 | An expression which determines the last value of the counter variable for which the loop should be executed. |
| expr3 | An expression which determines the value indicating the increment of the counter variable each time the loop has been executed. |
| condition | a logical expression evaluating to True or False. |
| statements | Any group of one or more Qlik Sense script statements. |
Example 1: Loading a sequence of files
// LOAD files file1.csv..file9.csv
for a=1 to 9
LOAD * from file$(a).csv;
next
Example 2: Loading a random number of files
In this example, we assume there are data files x1.csv, x3.csv, x5.csv, x7.csv and x9.csv. Loading is stopped at a random point using the if rand( )<0.5 then condition.
for counter=1 to 9 step 2
set filename=x$(counter).csv;
if rand( )<0.5 then
exit for unless counter=1
end if
LOAD a,b from $(filename);
next