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yyyymm_to_yyyyfrac

Converts a one dimensional array containing yyyymm values to yyyy and fractional year.

Prototype

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"  ; This library is automatically loaded
                                                             ; from NCL V6.2.0 onward.
                                                             ; No need for user to explicitly load.

	function yyyymm_to_yyyyfrac (
		yyyymm    [*] : integer, float, double,  
		mm_offset [1] : float or double          
	)

Arguments

yyyymm

A one dimensional array containing yyyymm values. The "mm" must range from 1 to 12 corresponding to January to December.

mm_offset

A scalar denoting the monthly offset. A value of 0.0 yields fractional values starting at 0.0. A values of 0.5 yields mid-month fractional values.

Return value

A one dimensional array containing values of the form yyyy plus fractional part of year. If either yyyymm or mm_offset is type double the return will be type double. Otherwise type float is returned.

Description

For each month of each year, the values yyyymm=yyyy*100+(mm-1)/12 or yyyymm=yyyy*100+((mm-mm_offset)-1)/12 are returned. For "mm" values spanning 1 through 12, the fractional parts are:

            mm_offset  mm_offset
       mm      0.0        0.5
       __   _________  _________
        1   0.0        0.0416667
        2   0.0833333  0.125
        3   0.166667   0.208333
        4   0.25       0.291667
        5   0.333333   0.375
        6   0.416667   0.458333
        7   0.5        0.541667
        8   0.583333   0.625
        9   0.666667   0.708333
        10  0.75       0.791667
        11  0.833333   0.875
        12  0.916667   0.958333
This function is most frequently used for plotting, say, time series.

See Also

List of "date" and "calendar" functions

Examples

The following requires that contributed.ncl be loaded prior to invoking the function.

 load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
 

Example 1

Convert a 1D array, yyyymm = (/ 197901 , 198407, 200112 /), to yyyy and fractional year.

  yrfrac = yyyymm_to_yyyyfrac(yyyymm, 0.0)
  YRFRAC = yyyymm_to_yyyyfrac(yyyymm, 0.5)
print(yrfrac+" "+YRFRAC))
Each of the above yields a 1D array of length 3 values.
    1979      1979.04
    1984.5    1984.54
    2001.92   2001.96
Example 2

Create a 1D "yyyymm" array and convert to yyyy and a fractional part.

    TIME = yyyymm_time(1901, 2001, "integer")
    yyyyFrac = yyyymm_to_yyyyfrac(TIME, 0.0)
    print(yyyyFrac) 
The above returns a 1D array of length 1212 values.
Variable: yyyyFrac
Type: float
Total Size: 4848 bytes
            1212 values
Number of Dimensions: 1
Dimensions and sizes:   [time | 1212]
Coordinates: 
            time: [190101..200112]
Number Of Attributes: 2
  units :       YYYY + fractional portion of year
  NCL : derived using function yyyymm_to_yyyyfrac
(0)     1901
(1)     1901.083
(2)     1901.167
(3)     1901.25
(4)     1901.333
[snip]
(1206)  2001.5
(1207)  2001.583
(1208)  2001.667
(1209)  2001.75
(1210)  2001.833
(1211)  2001.917