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nice_mnmxintvl

Calculates "nice" values for endpoints and spacing to be used for creating a series of equally-spaced levels through the data domain.

Prototype

	function nice_mnmxintvl (
		cmin       [1] : numeric,  
		cmax       [1] : numeric,  
		max_levels [1] : integer,  
		outside    [1] : logical   
	)

	return_val [3] :  numeric      ; float or double

Arguments

cmin
cmax

Minimum and maximum values of your data.

max_levels

The maximum number of levels you want.

outside

Controls whether the "nice" values returned fall just outside or just inside the input cmin and cmax values.

Description

Given the minimum and maximum values of a data domain and the maximum number of levels desired, this function calculates "nice" values for endpoints and spacing. The returned values can be used to create a series of "nice" equally-spaced levels through the data domain. The outside flag controls whether the returned "nice" min and max values are inside or outside the data range.

An array of three elements of type float (or double if cmin and/or cmax are double) is returned where the first element contains the "nice" minimum value, the second element the "nice" maximum value, and the third element the spacing. If cmin or cmax is a missing value, then a missing value will be returned.

See Also

symMinMaxPlt

Examples

Example 1

Assume data is dimensioned ny x nx. Determine consistent "nice" minimum and maximum values and a nice contour interval (that falls inside the original min/max range) to use for contour plots: 

  dmin    = min(data)
  dmax    = max(data)
  maxlev  = 18
  mnmxint = nice_mnmxintvl( dmin, dmax, maxlev, False)

  res = True
  . . .
  res@cnLevelSelectionMode = "ManualLevels"
  res@cnMinLevelValF       = mnmxint(0)
  res@cnMaxLevelValF       = mnmxint(1)
  res@cnLevelSpacingF      = mnmxint(2)

Example 2

Assume data is dimensioned ntim x klvl ny x nx. Determine consistent "nice" minimum and maximum values and a nice contour intervals for each level to use for contour plots. Use NCL's new statement and typeof function to allocate memory. 

  maxlev = 10
  mnmxint = new( (/klvl,3/), typeof(data) ) 
  do kl=0,klvl-1
     dmin   = min( data(:,kl,:,:) )
     dmax   = max( data(:,kl,:,:) )
     mnmxint(kl,:) = nice_mnmxintvl( dmin, dmax, maxlev, True)
  end if
mnmxint will contain different "nice" min, max and contour intervals for each level.

Example 3

Assume x1-x4 and y1-y4 are dimensioned as follows: [x1(N),y1(N)], [x2(M),Y2(M)], [x3(K),y3(5,K)], and [x4(3,L),y4(3,L)]. Assume that a common set of "nice" x-y min/max values is desired for 4 different plots: 

  minX     = min( (/ min(x1), min(x2), min(x3), min(x4) /) )
  minY     = min( (/ min(y1), min(y2), min(y3), min(y4) /) )

  maxLev   = 10
  mnmxintX = nice_mnmxintvl( minX, maxX, maxLev, True)
  mnmxintY = nice_mnmxintvl( minY, maxY, maxLev, True)

An array of 3 elements is returned which can be used to set specific NCL graphic resources. For example, you could use these values to set the following XY plot resources: 

  res@trXMinF  = mnmxintX(0)
  res@trXMaxF  = mnmxintX(1)
  res@trYMinF  = mnmxintY(0)
  res@trYMaxF  = mnmxintY(1)