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This gem runs in .

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Overview

Use the Reformat gem to:
  • rename columns
  • create calculated columns
  • modify existing column values
  • change data types
  • select which columns appear in the output dataset
Use expressions and functions to transform values, combine columns, clean data, or create new derived fields.
The gem has a corresponding interactive gem example. See Interactive gem examples to learn how to run sample pipelines for this and other gems.

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Common transformation examples

GoalExample expression
Rename a columnSet Target column to the new column name
Create a full name column`first_name’ ‘last_name`
Convert text to uppercaseUPPER(customer_name)
Replace null valuesCOALESCE(region, 'Unknown')
Create a calculated fieldprice * quantity
Convert a value to a stringCAST(order_id AS STRING)
Extract part of a dateYEAR(order_date)

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Parameters

ParameterDescriptionRequired
ModelInput dataset to transformTrue
Target columnOutput column nameFalse
ExpressionExpression to compute target columnRequired if a Target column is present
If no columns are selected, then all columns are passed through to the output.

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How Reformat works

The Reformat gem processes each row individually and applies expressions to generate output columns. You can:
  • keep existing columns
  • rename columns
  • modify column values
  • create new columns
  • remove unwanted columns
If no columns are selected, all input columns are passed through unchanged.

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Common issues

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Column not found

Verify that:
  • the column name exists in the input dataset.
  • the column name uses the correct capitalization.
  • the column reference is spelled correctly.

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Type mismatch errors

Some functions and operators require specific data types. For example:
  • numeric calculations require numeric columns.
  • string functions require text values.
Use CAST() to convert values when needed.

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Null values causing unexpected results

Some expressions return NULL when one or more input values are NULL. Use COALESCE() to replace null values with defaults.

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Duplicate column names

Output column names must be unique.

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Similar tools and concepts

The Reformat gem can be used to:
  • rename columns
  • create calculated fields
  • modify existing column values
  • select output columns
You may recognize similar behavior from:
  • SQL SELECT expressions and aliases
  • the Alteryx Formula and Select tools
  • PySpark select() and withColumn()
  • Pandas column transformations