String and math expressions

Data Transformation in KNIME

Mahantesh Pattadkal

Sr. Data Scientist

Expression-based transformation

• Allows applying custom logic
• Manipulate data with expressions
• Simple arithmetic to complex string manipulations

Formulating an expression

An expression can be formulated by

• Using operators

• Using functions

• Combination of operators and functions

Expression Node

$$

$$ $$ $$

• Functions for string manipulation
• Math formulas
• Use a range of operators
• Create or replace a new column

String expressions

• Perform simple and complex string manipulations
• Use one or more string functions

Example

replace("I loved the m@vie", "@", "o")

Output

I loved the movie

Popular string functions

Popular string functions

Popular string functions

Math expressions

• Perform mathematical transformation

• Use math operators or functions and formulas

Example

max(20, 30, 70+5)

Output

75

Popular math functions

Popular math functions

Popular math functions

Mixed expressions

• Perform string and mathematical transformation.

• Use math and string functions together.

Example

Add a comment column

Mixed expressions

Calculate minimum value

Syntax

min(column1, column2)

Expression

min($Val1$, $Val2$)

Convert it to string format

Syntax

string(input)

Expression

string(min($Val1$, $Val2$))

Mixed expressions

Syntax

join(separator, string1, string2)

Expression

join(" ", "The minimum value is", string(min($val1$,$val2$)))

Output Comment column

The minimum value is 20

Let's practice!

Data Transformation in KNIME