CONCAT() Function: combine several variables

The CONCAT() function combines multiple values into a single string. It is useful for constructing clinically meaningful composite variables from existing data.

It can be used with:

• List (categorical) variables

• Numeric variables

• Event variables

• As part of a sub-expression inside another function

Syntax

CONCAT(value1, value2, ...) 

All inputs are converted to text and concatenated in order.

Clinical Examples

1️⃣ Combining categorical variables

• Side = Right

• TearSeverity = Massive

CONCAT(Side, TearSeverity) 

Result:

RightMassive 

Important note: For List variables, a new modality RightMassive is automatically created if it does not already exist.

2️⃣ Combining numeric variables

CONCAT(1, 2)

Result:

12 

3️⃣ Building a date string from numeric fields

If you store:

• Day (numeric)

• Month (numeric)

• Year (numeric)

You can write:

EVENT(CONCAT(Day, '/', Month, '/', Year)) 

This creates a properly formatted date string that can be used inside another function such as EVENT().

Key Points

• If used in a list dynamic variable, new concatenated modalities are created automatically.

• It can be nested inside other expressions.