Y201: Find Histogram-Channel

Author(s): J. Zoll, P. Rastl	Library: KERNLIB
Submitter: C. Letertre	Submitted: 01.09.1969
Language: Fortran or Assembler	Revised: 16.09.1991

IUCHAN, IUBIN, IUHIST all find the histogram-channel for a given quantity in the same way. They differ only slightly in the way in which the parameters are passed.

Structure:

FUNCTION subprograms
User Entry Names: IUCHAN, IUBIN, IUHIST

Usage:

All routines need the the following parameters:

X

(REAL) Quantity to be histogrammed.

XLOW

(REAL) Lower limit of the histogram.

DX

(REAL) Channel width.

NX

(INTEGER) Number of channels.

and they return the channel number normally, or for underflow ( ), or for overflow ( ).

is a small bias to counteract rounding effects when X is exactly on a bin edge, a likely and serious problem when compressed data are histogrammed.

on 32-bit machines, on machines with a larger word size.
Function IUCHAN:

    N = IUCHAN(X,XLOW,DX,NX)

Functions IUBIN and IUHIST:

    DIMENSION PAR(3)
    EQUIVALENCE(NX,PAR(1))
    LOGICAL SPILL
 
    N = IUBIN (X,PAR,SPILL)
    N = IUHIST(X,PAR,SPILL)

with

PAR

Histogram parameters:

(for IUBIN), or reciprocal of the channel width (for IUHIST).

SPILL

(LOGICAL) Flag set to .TRUE. or .FALSE. depending on whether X is outside or inside the histogram.