Name

---

  MGH_LOCATE

Purpose

---

  This function calculates translates positions in physical space into
  the "index space" of a 1D vector.

Calling Sequence

---

  Result = MGH_LOCATE(xin)

Positional Parameters

---

  xin (input, 1-D numeric array)
    X positions of the vertices of the input grid. The X values
    should be monotonic (if not, results will be unpredictable);
    they need not be uniform.

Keyword Parameters

---

  The following keywords define the locations in physical space of
  the output grid, cf. the GRIDDATA routine: DELTA, DIMENSION, START, XOUT.
  In addition:
    EXTRAPOLATE (input, switch)
      Set this keyword to cause output locations outside the
      range of input values to be determined by extrapolation.
    MISSING (input, numeric scalar)
      Value used for locations outside the range of input
      values. Ignored if the EXTRAPOLATE keyword is set.
      Default is NaN.
    SPLINE (input, switch)
      Set this keyword to use spline interpolation; default is linear.
      Setting both the SPLINE and EXTRAPOLATE keywords together
      causes an error.

Return Value

---

  The function returns a floating array representing the output
  location as fractional indices on the grid represented by
  XIN. The result has the same dimensions as the output locations.

Procedure

---

  Construct variable representing position in i direction &
  interpolate.
###########################################################################
  This software is provided subject to the following conditions:
  1. NIWA makes no representations or warranties regarding the
    accuracy of the software, the use to which the software may
    be put or the results to be obtained from the use of the
    software. Accordingly NIWA accepts no liability for any loss
    or damage (whether direct of indirect) incurred by any person
    through the use of or reliance on the software.
  2. NIWA is to be acknowledged as the original author of the
    software where the software is used or presented in any form.
###########################################################################

Modification History

---

  Mark Hadfield, 2002-07:
    Written.
  Mark Hadfield, 2003-01:
    Now calls IDL library routine INTERPOL instead of MGH_INTERPOL.
  Mark Hadfield, 2004-03:
    Added SPLINE keyword.