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

randbit(file, dbib, dbob, density, dbsn, dbsd)

Name	Type	Caption	Length	Value range
FILE *	str	Input file name	1 -
DBIB	List[int]	Input bitmap segment	0 -
DBOB	List[int]	Output bitmap segment	0 -
DENSITY *	List[float]	Random sampling density (%)	1 - 1	0 - 100
DBSN	str	Output bitmap segment name	0 -	Default: RANDMASK
DBSD	str	Output bitmap segment description	0 -

* 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.

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.

Note: If the input bitmap (DBIB) and output bitmap (DBOB) parameters are defaulted, one output bitmap with the specified DENSITY will be generated.

Duplicate bitmap segments are NOT allowed.

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.

Note: The segment name can be changed using MAS.

DBSD

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

Note: The segment descriptor can be changed using MAS.

Return Value

Returns: Last Segments Created

Type: PCI_INT

Returns the output segments created.

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.

from pci.randbit import randbit

file	=	r"/demo/irvine.pix"
dbib	=	[9]
dbob	=	[]
density	=	[50]
dbsn	=	""
dbsd	=	""

mask	=	randbit(file, dbib, dbob, density, dbsn, dbsd)

References

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

Environments	PYTHON :: EASI :: MODELER
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