Module: Histogram ()

Description:

This module computes the histogram of the data values of a scalar field, line set, point cloud or spreadsheet, and plots it in a separate plot window. In addition, the mean value, the standard deviation and root mean square (rms) are printed.

Press the Apply button to start the computation of the histogram and pop up the plot window containing it. The bin (interval) is computed in function of the Range port and the maximum number of bins (See the Max Num Bins port description). The count value depend of the distribution of numerical data between each interval.

Connections:

Data [required]
The scalar field to be investigated. Regular fields, fields defined on tetrahedral or hexahedral grids, and fields defined on surfaces are supported. Furthermore, you may connect line sets and spreadsheets to this port.

ROI [optional]
Connection to a module providing a region-of-interest ROI Box. If such a module is connected, only the volume within the ROI is evaluated in the histogram.

Labels [optional]
A uniform label image which can be used to restrict the histogram to a certain material.

Ports:

Info


Prints the mean value, the standard deviation and root mean square (rms) of all input data values once the histogram has been computed. Both info ports are only shown when the Apply button has been pressed, i.e., the histogram has been computed.

Range

Defines the data range over which the histogram is to be computed. The Reset button adjusts the data range so that it completely covers the values of the input object.
Note that this range is synchronized with the plot X-axis range: modifying this range will change the plot X-axis minimum and maximum values and, vice-versa, panning or zooming on the plot X-axis will update this port. The bin does not change until the histogram has been computed (Pressing the Apply button).

Max Num Bins

Defines the maximum number of bins (intervals) the data range is divided into. The effective number of bins will be determined as the minimum value between the maximum number of bins and the histogram range difference (defined within the Range port). The histogram counts the number of data values falling in each bin. In the case of integer input values, i.e., bytes, shorts, or ints, the number of bins is internally adjusted so that all bins have the same integer width. This is required in order to avoid aliasing effects.

Histogram Options

• absolute the absolute frequencies are displayed.
• relative the relative frequencies i.e., the absolute frequencies divided by the number of events (voxels, tetrahedra,...) are shown.
• in % displays relative frequencies as a percentage of events.
• + cumulative displays additionally the cumulative frequencies as a line graph.

Plot Options

If the line drawing toggle is set, the histogram is plotted as a line instead of a histogram. With the logarithmic toggle set, the plot is shown with logarithmic scaling [Default].

Threshold

Defines a threshold value and displays the percentage of all data values which lie above the given threshold. The percentage corresponds to the given range. The threshold value is shown as a yellow vertical markerline in the plot window. This markerline can be moved within the plot window by pressing the left mouse button over the markerline and moving it to the new position. The new position is then taken as the new threshold value. The computation and display of the threshold value can be toggled on or off. This port is only shown when the histogram has been computed.

Tindex

The tindex value defines a reversed threshold value, i.e., a tindex of 90 returns the value where 90% of the data values lie above that value. It is denoted by the reddish markerline in the plot window. The computation and display of the index value can be toggled on or off. This port is only shown when the histogram has been computed.

Material

If a label image is connected to the port Labels and the input data field is a regular scalar field, this port provides the opportunity to compute the histogram for one material only. Otherwise, it is hidden.

Data

If a line set is used as input, then this port provides the opportunity to select the data channel for which the histogram is to be computed. You may also compute the histogram for the coordinates of the line set.

Table

If a spreadsheet is used as input, this port lets you select the table in which the data channels will be searched for. Note that this port will only be visible if the spreadsheet contains more than one table.

Data Channel

If a spreadsheet is used as input, this port lets you select the data channel for which the histogram is to be computed.

Data

If a point cloud is used as input, this port lets you select the data channel for which the histogram is to be computed.

Commands:

showCumulative [{0|1}]
Switches the display of a cumulative plot on (1 (Default)) or off (0).

showRightCumulative [{0|1}]
Switches the display of a right cumulative plot on (1 (Default)) or off (0).

showDifferential [{0|1}]
Switches the display of a differential plot on (1 (Default)) or off (0). If there is a differential plot to be shown the axis scaling is switched to linear, since there might be negative values.