IBM Visualization Data Explorer User's Reference

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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:

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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