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maxind

Returns the index of the first occurrence of a maximum value.

Prototype

	function maxind (
		arg [*] : numeric   
	)

	return_val [1] :  integer or long

Arguments

arg

A one-dimensional numeric array.

Description

This function scans an array for the maximum value and returns the index of the first occurrence of it. Missing values are ignored. Remember that in NCL, indexing starts at 0, not 1.

As of version 6.0.0, this function will return a long if on a 64-bit system and the index value is >= 2 GB.

See Also

minind, min, max, ind_resolve, dim_min, dim_max, dim_min_n, dim_max_n

Examples

Example 1

   x = (/3.,2.,5.,1.,5.,2.,5.,1.,3.,2./)
   i = maxind(x)                           ; Should be 2.

Example 2

Find the index of the maximum value in a multi-dimensional array.

;---Create a dummy 2 x 2 x 4 array.
  a = (/(/(/1,2,3,4/), (/5,6,7,8/)/), (/(/9,1,9,8/),(/7,6,1,4/)/)/)

;---Convert to 1D
  a1D      = ndtooned(a)
  dsizes_a = dimsizes(a)

;---Resolve the 1D indices back to their original 3D array.
  indices  = ind_resolve(maxind(a1D),dsizes_a)
  print(indices)

Example 3

Find the latitude and longitude location of the maximum value in a two dimensional array.

;---X is a two dimensional array dimensioned lat x lon
  dims = dimsizes(X)
  x1d = ndtooned(X)      ; convert 2D array to 1D for use in maxind
  inds = ind_resolve(maxind (x1d), dims)    ; convert 1D array back to 2D 
  ilat = inds(0,0)        ; select the latitude index where the X array is at its' maximum  
  ilon = inds(0,1)        ; select the longitude index where the X array is at its' maximum
  lat_max = X&lat(ilat)   ; insert the latitude index into the lat coordinate variable
  lon_max = X&lon(ilon)   ; insert the longitude index into the lon coordinate variable
  print("Maximum value located at "+lat_max+", "+lon_max)