SURFLIB_HISTOGRAM_GRID - Calculate a 2-D histogram of I,J coordinates on a grid

Description:

Given an array of I,J coordinates calculate the histogram of all points onto this grid of size NX $*$ NY. Just tells you how many data points there are per cell. Returns the histogram and the highest value in the histogram

Invocation:

CALL SURFLIB_HISTOGRAM_GRID (N_PTS, NX, NY, USEDATA, IN_DATA, IN_QUALITY, BADBIT, IJ, GRID, IMAX, JMAX, NMAX, STATUS )

Arguments:

N_PTS = INTEGER (Given)

Number of I,J pairs supplied

NX = INTEGER (Given)

Size of X dimension

NY = INTEGER (Given)

Size of Y dimension

USEDATA = LOGICAL (Given)

If TRUE the histogram takes bad data points into account by not including them in the histogram. If false the straight histogram of the I,J's is constructed.

IN_DATA(N_PTS) = REAL (Given)

Input data

IN_QUALITY(N_PTS) = BYTE (Given)

Input quality

BADBIT = BYTE (Given)

Bad bits mask for quality array

IJ ( 2, N_PTS ) = INTEGER (Given)

Positions of each point (I,J) in output grid

GRID (NX, NY) = INTEGER (Given & Returned)

Histogram. Note that array is not cleared by this routine leaving the possibility that the routine can be called multiple times to include more than one data set.

IMAX = INTEGER (Returned)

I position of maximum [first one encountered]

JMAX = INTEGER (Returned)

J position of maximum [first one encountered]

NMAX = INTEGER (Returned)

Maximum value in histogram

STATUS = INTEGER (Given & Returned)

Global Status

Notes:

• If USEDATA is TRUE the data and quality array are used so that bad pixels can be identified and not included into the histogram of positions.

• GRID is not initialised by this routine

• A warning error is raised if the bounds of the histogram are exceeded. It is up to the caller to decide whether this is a fatal error.

Copyright

Copyright ©1995,1996,1997,1998,1999 Particle Physics and Astronomy Research Council. All Rights Reserved.