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#### A.4.5.15 Histogram Form

Histogram form configuration panel

The Histogram form () plots a histogram generated by binning samples along the X axis.

This form may be used in either the Histogram or Plane plot windows.

These options always appear in the form configuration panel:

Colour
  Selects the basic colour for the dataset.
Transparency
  Adjusts the transparency of the bars or line. For bar styles which are already partially transparent, this fades them further.
Bar Form
  Type of histogram bars: filled, open, steps, spikes etc.
Thickness
  Controls line thickness where applicable. This is only relevant for bar styles that draw a finite thickness line, so has no effect for solid bars.
Dash
  Controls the dash pattern of the line (solid, dots, dashes etc). This is only relevant for bar styles that draw a finite thickness line, so has no effect for solid bars.

And these options appear in the form configuration panel for the Plane window, or the Bins control () for the Histogram window:

Bin Size
  A scale for the width of bins that are shown on the screen. There are two ways to specify this. If the left-hand radio button is selected, the adjacent slider will adjust the bin size, which is also affected by the actual width of the plotting window in pixels. Slide the slider left to get narrower bins or right to get wider ones. If the right-hand radio button is selected, you can enter a numeric value giving the actual width in data units of each bar (for a logarithmic X axis this value is a factor).
Bin Phase
  Controls where the horizontal zero point for binning is set. For instance if your bin size is 1, it controls whether bins boundaries are at 0, 1, 2, .. or 0.5, 1.5, 2.5, ... etc. If the slider is at either end of the scale, there will be a bin boundary at X=0 (linear X axis) or X=1 (logarithmic X axis).
Cumulative
  If true, the histogram bars plotted are calculated cumulatively; each bin includes the counts from all previous bins.
Normalise
  Defines how, if at all, the bars are normalised. The available options are:
  - none: No normalisation is performed.
  - area: The total area of histogram bars is normalised to unity. For cumulative plots, this behaves like height.
  - maximum: The height of the tallest histogram bar is normalised to unity. For cumulative plots, this behaves like height.
  - height: The total height of histogram bars is normalised to unity.

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk