IBM Visualization Data Explorer User's Reference

Histogram

Category

Transformation

Function

Constructs a histogram from input data and computes the median.

Syntax

histogram, median = Histogram(data, bins, min, max, out);

Inputs

Name	Type	Default	Description
data	scalar list or vector list or scalar field or vector field or series	none	field to be operated on
bins	integer or vector	256 for bytes, 100 otherwise	number of bins in histogram
min	scalar or vector or field	min. of data	minimum value to operate on
max	scalar or vector or field	max. of data	maximum value to operate on
out	flag or vector	0	0: exclude out-of-range values 1: include out-of-range values

Outputs

Name	Type	Description
histogram	field or series	the histogram
median	scalar	median of the input data

Functional Details

The median is determined from an interpolation performed in the bin containing the median element (or elements, if there are an even number of samples).

data	is the data whose frequency distribution is to be computed and then represented in a histogram. data can consist of scalars, 2-vectors, or 3-vectors, with resulting one-dimensional, two-dimensional, or three-dimensional histograms, respectively.
bins	specifies the number of bins into which the range from min to max will be divided. If data consists of vectors, then bins can be a vector of the same length specifying the number of bins in each dimension.
min  and  max	specify the range of values for which the histogram is computed. If neither parameter is specified, the values used are the minimum and maximum of the input data values. If min is a scalar value, it is the value used. 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. If data consists of vectors, then min and max may also consist of vectors of the same length to specify the range in each dimension. Otherwise, the values given for min and max will apply to each dimension.
out	specifies whether the module ignores data values outside the range of min and max or includes them in the first and last bins respectively. If data consists of vectors, then out may be a vector of the same length specifying how to treat each dimension.

Notes:

1. For the output, a "positions" component is constructed that consists of bins +1 points, corresponding to the boundaries between bins.

2. A regular "connections" component is constructed that consists of a set of line segments connecting the end points.

3. The "data" component, which is connection dependent, contains the counts for the corresponding bin.

4. The interval for each bin is closed on the min side and open on the max side. To include the maximum data value:
   • set out to include outlying values

     or

   • set max to a value slightly larger than the maximum data value.

To see the results of Histogram for scalar data, pass its output to the Plot module. For 2-vector data, pass its output to the RubberSheet module with a scale factor of 1. For 3-vector data, use either the Isolate module or use Include followed by ShowBoundary.

Components

Creates new "positions," "connections," and "data" components. The data, representing the number of items in each bin, is connections dependent.

Example Visual Program

UsingEqualize.net
SIMPLE/Histogram.net

See Also

 Equalize,  Plot,  Scale

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