PHP's gd library is missing or unable to create PNG images

# Calc Histogram

## Description

This functor calculates a histogram from a map.

## Inputs

Name | Type | Description |
---|---|---|

Map | Map Type | Any map |

## Optional Inputs

Name | Type | Description | Default Value |
---|---|---|---|

Interval Width | Real Value Type | The width of the histogram interval. | 1.0 |

Cumulative | Boolean Value Type | If true, the calculated histogram is cumulative. | False |

Relative | Boolean Value Type | If true, the values in the histogram are normalized by the total number of occurrences. | False |

## Outputs

Name | Type | Description |
---|---|---|

Histogram | Lookup Table | The calculated histogram. |

## Notes

It also possible to calculate a histogram relative to the cumulative values. To do this, set both input flags (“Cumulative” and “Relative”).

When the “Interval Width” is different from one, the input values are remapped according to the expression below to speed up the calculation.

, where *value2* is the resulting value, *value* is the value present in the input map and *width* is the “Interval Width”.

Because of the remapping, the lower limit of the resulting histogram can be lower than the minimum value in the input map. The upper limit of the histogram can be greater than the maximum value in the input map.

## Group

## Internal Name

CalcHistogram