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The `numpy.ma` module

# Masked arrays

Masked arrays are arrays that may have missing or invalid entries. The `numpy.ma` module provides a nearly work-alike replacement for numpy that supports data arrays with masks.

- The `numpy.ma` module
  - Rationale
  - What is a masked array?
  - The `numpy.ma` module
- Using numpy.ma
  - Constructing masked arrays
  - Accessing the data
  - Accessing the mask
  - Accessing only the valid entries
  - Modifying the mask
  - Indexing and slicing
  - Operations on masked arrays
- Examples
  - Data with a given value representing missing data
  - Filling in the missing data
  - Numerical operations
  - Ignoring extreme values
- Constants of the `numpy.ma` module
- The `MaskedArray` class
  - Attributes and properties of masked arrays
- `MaskedArray` methods
  - Conversion
  - Shape manipulation
  - Item selection and manipulation
  - Pickling and copy
  - Calculations
  - Arithmetic and comparison operations
  - Representation
  - Special methods
  - Specific methods
- Masked array operations
  - Constants
  - Creation
  - Inspecting the array
  - Manipulating a MaskedArray
  - Operations on masks
  - Conversion operations
  - Masked arrays arithmetics