# IBM Visualization Data Explorer User's Reference

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### Equalize

Category

Transformation

Function

Applies histogram equalization to a field.

Syntax

    equalized = Equalize(data, bins, min, max, ihist, ohist);

Inputs

Name | Type | Default | Description
--- | --- | --- | ---
`data` | scalar field | none | data to be equalized
`bins` | integer | input dependent | number of equalization bins
`min` | scalar or field | min of data | lower bound of equalization
`max` | scalar or field | max of data | upper bound of equalization
`ihist` | field | histogram of data | input distribution
`ohist` | field | uniform distribution | output distribution

Outputs

Name | Type | Description
--- | --- | ---
`equalized` | scalar field | histogram-equalized data

Functional Details

This module equalizes an input data field so that the histogram of the output approximates a specified distribution (`ohist`), which by default is a uniform distribution.

If `data` specifies a series, the histogram of the entire series is used to construct the probability distribution, which is then applied to each field in the series.

`data` | is the scalar data field to be equalized.
`bins` | is the number of bins to be used in creating the equalization histogram. The default value is 100, unless `data` consists of byte values. In that case, the default is: `max` - `min` + 1
`min` and `max` | specify the range of the data values to be equalized. Values outside that range remain unchanged. Notes: If neither parameter is specified, the values used are the minimum and maximum of the input field. If `min` is a scalar value, it is the minimum value equalized. If `min` is a data field, the minimum data value of that field is used. `max` is similarly interpreted. If `min` is a data field and `max` is unspecified, the module uses the minimum and maximum values of that field.
`ihist` | is the histogram used to determine the equalization function required, and by default it is the histogram of `data`. If `ihist` is specified explicitly and the number of bins specified does not match the number in the histogram, the module resamples the histogram so that it contains the specified number.
`ohist` | is the type of output histogram desired. By default, the module equalizes to a uniform distribution. You can equalize to some other distribution by specifying an appropriate histogram for this parameter.

Note: A well-formed histogram (for `ihist` and `ohist`) consists of a field with a "positions" component that defines the bins of the histogram; a "connections" component that connects the positions; and a "data" component that contains the number of items in each bin. The data should be connection dependent ("dep" "connections").

Components

Equalize modifies the data component. All other components are unmodified.

Example Visual Programs

    UsingEqualize.net

See Also

Filter, Morph, Histogram

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