RANDBIT

Description

Generates a bitmap mask that can be used for random sampling. A bitmap is generated with a specified bit density. The bitmap may be based on a subsample of an existing bitmap, or on a sample of the whole image space.

Parameters

Name	Type	Caption	Length	Value range
FILE *	String	Input file name	1 - 192
DBIB	Integer	Input bitmap segment	0 -
DBOB	Integer	Output bitmap segment	0 -
DENSITY *	Float	Random sampling density (%)	1 - 1	0 - 100
DBSN	String	Output bitmap segment name	0 - 192	Default: RANDMASK
DBSD	String	Output bitmap segment description	0 - 192
MONITOR	String	Monitor mode	0 - 3	ON, OFF Default: ON

* Required parameter

Parameter descriptions

FILE

Specifies the name of the GDB-supported file containing input bitmaps, and to which the output bitmaps will be written.

DBIB

Specifies the image bitmaps to serve as sample masks for the output bitmaps.

Duplicate segments are allowed.

Ranges of channels or segments can be specified with negative values. For example, {1,-4,10} is internally expanded to {1,2,3,4,10}. When you are not specifying a range in this way, only 48 numbers can be specified explicitly.

DBOB

Specifies the output bitmap to receive the sample results.

The output bitmap may be the same as the input bitmap; if this parameter is not specified, new bitmap segments are created.

Duplicate bitmap segments are NOT allowed.

Ranges of channels or segments can be specified with negative values. For example, {1,-4,10} is internally expanded to {1,2,3,4,10}. When you are not specifying a range in this way, only 48 numbers can be specified explicitly.

DENSITY

Specifies the density, in percentage, at which to sample the output bitmap mask.

If set to 100 (percent), the output bitmap will be 1 (all pixels on) everywhere the input bitmap is 1 (or everywhere, if there is no input bitmap). If set to 50, approximately half the output bits will be 1.

DBSN

Specifies a name (up to 8 characters) for the output bitmap segment. If this parameter is not specified, the default name RANDMASK is used.

DBSD

Describes (in up to 64 characters) the contents or origins of the output neural network segment.

MONITOR

The program progress can be monitored by printing the percentage of processing completed. A system parameter, MONITOR, controls this activity.

Available options are:

• ON: Turns the monitor ON (default)
• OFF: Turns the monitor OFF (recommended if running in batch or background mode)

Details

RANDBIT generates a mask to be used for random sampling. An output bitmap suitable for use with other "maskable" functions is generated, based on a specified sampling density (DENSITY) and an input bitmap mask (DBIB).

The input bitmap parameter (DBIB) specifies the input masks from which to compute a sub-sample space. If an input bitmap is not provided, the entire image space will be sampled.

Example

Generate a sub-sample of the "Water1" training mask from irvine.pix. This can then be used to generate a signature, and the resulting classification can be compared to that generated by the original training mask.

EASI>file	=	"/demo/irvine.pix"
EASI>dbib	=	9
EASI>dbob	=	
EASI>density	=	50
EASI>dbsn	=
EASI>dbsd	=

EASI>RUN RANDBIT

References

Law & Kelton, "Simulation Modelling and Analysis", P449.