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yyyymm_to_yyyyfrac

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

Available in version 4.2.0.a033 or later.

Prototype

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

	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" 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

yyyymm_time

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 to yyyymm yyyymm = (/ 197901 , 198407, 200112 /)

  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 covert 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