Calculates individual accumulated sums of sequences ('runs') of a specified length.
Available in version 6.2.1 and later.
function dim_acumrun_n ( x : numeric, lrun  : integer, opt : integer, dims [*] : integer ) return_val [dimsizes(x)] : float, double (int, long, float, double in NCL V6.4.0 and later)
A variable of numeric type and any dimensionality. NOTE: If there is no explicit _FillValue associated with x, the default _FillValue will be used.lrun
A scalar specifying the length of the run. lrun must be greater than or equal to 2.opt
A scalar indicating how an individual run with _FillValue are handled. The default is opt=0.
- opt=0: if a _FillValue is encountered, set the current accumulated run value to _FillValue.
- opt=1: if a _FillValue is encountered, continue calculating the accumulated sum using available values.
The dimension(s) of x on which to calculate the sum. Must be consecutive and monotonically increasing.
In NCL Versions 6.3.0 and earlier, this routine returned either a float or double of the same dimensions as x.
In later versions of NCL, it was enhanced to return the following:
- double if x is double
- float if x is float
- long if x is long
- integer if x is any other type
The dim_acumrun_n function calculates the cumulative sum of the current values and the previous (lrun-1) values. This type of calculation is often done for precipitation values to assess drought.
Example 1: Calculate the accumulated individual running sums of the current and previous (lrun-1i) values. When no _FillValue are encountered opt=0 and 1 yield the same answer.
x = (/1,2,3,4,5,7,-23/) x@_FillValue = -999 x_ars = dim_acumrun_n(x,3,0,0) ; (/-999,-999, 6, 9, 12, 16, -11 /) x_ars = dim_acumrun_n(x,3,1,0) ; (/-999,-999, 6, 9, 12, 16, -11 /)Example 2: When one or more _FillValue are encountered, opt=0 and 1 yield different results.
x = (/1,2,-999,4,5,7,-999, 2, -9, 5/) x@_FillValue = -999 x_ars = dim_acumrun_n(x,3,0,0) ; (/-999,-999,-999,-999,-999, 16,-999,-999,-999, -2 /) x_ars = dim_acumrun_n(x,3,1,0) ; (/-999,-999, 3 , 6 , 9 , 16, 12 , 9 , -7 , -2 /)