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dim_standardize_n

Calculates standardized anomalies of the given dimension(s) at all other dimensions.

Prototype

	function dim_standardize_n (
		x        : numeric,  
		opt      : integer,  
		dims [*] : integer   
	)

	return_val [dimsizes(x)] :  float or double

Arguments

A variable of numeric type and any dimensionality.

opt

Setting opt=1 means to use the population standard deviation (i.e., divide by the number of non-missing value [N]). Otherwise, the sample standard deviation is used for normalization (i.e., divide by [N-1]).

dims

The dimension(s) of x on which to calculate the standardized anomalies. Must be consecutive and monotonically increasing.

Return value

The output will be of type double if the input is double, and float otherwise.

The dimensionality will be the same as the input dimensionality.

Description

The dim_standardize_n function calculates and removes the mean from all elements of the dimensions indicated by dims. It then standardizes at these dimensions by dividing the resulting deviations from the mean by the standard deviation of the given dimensions. These values are often called standardized anomalies. This is repeated for each index of the remaining dimensions. Missing values are ignored.

Use the dim_standardize_n_Wrap function if metadata retention is desired. The interface is identical.

Examples

Example 1: Let x be a 1-dimensional array: (a) Create a new variable, xNew, that contains standardized values; (b) replace the variable x with the standardized values. Use the population standard deviation.

  xNew = dim_standardize_n(x, 1, 0)  ; new variable
  x    = dim_standardize_n(x, 1, 0)  ; Or, overwrite with deviations

  ; Use dim_standardize_n_Wrap if metadata retention is desired
  ; xNew = dim_standardize_n_Wrap(x, 1, 0)  ; new variable
  ; x    = dim_standardize_n_Wrap(x, 1, 0)  ; Or, overwrite with deviations

Note: when operating across the rightmost dimension, it is simpler to use dim_standardize.

Example 2: Let x be a 3-dimensional array with dimension sizes (ntim, nlat, nlon). Standardize values of the the rightmost (here, "nlon") dimension. Use the sample standard deviation.

   xLon = dim_standardize_n (x,0,2)        ; new variable
   x    = dim_standardize_n (x,0,2)        ; overwrite with deviations

   ; Use dim_standardize_n_Wrap if metadata retention is desired
   ; xLon = dim_standardize_n_Wrap (x,0,2)        ; new variable
   ; x    = dim_standardize_n_Wrap (x,0,2)        ; overwrite with deviations

Example 3: Let x be a 3-dimensional array with named dimensions (time, lat, lon) and dimension sizes (ntim, nlat, nlon). Standardize the values of the time dimension at all lat/lon indices:

   xTime = dim_standardize_n(x, 0, 0)

   ; Use dim_standardize_n_Wrap if metadata retention is desired
   ; xTime = dim_standardize_n_Wrap(x, 0, 0)

Example 4: Let x be a 4-dimensional array with named dimensions (time, lev, lat, lon) and dimension sizes (ntim, nlev, nlat, nlon). Standardize the values of the time and level dimension at all lat/lon indices:

   xstd = dim_standardize_n(x, 0, (/0,1/))

   ; Use dim_standardize_n_Wrap if metadata retention is desired
   ; xstd = dim_standardize_n_Wrap(x, 0, (/0,1/))

Example 5: Let x be as in Example 3 and let x contain monthly means for (say) 10 years of data (ntim=120). Standardized monthly anomalies for each month could be calculated using array subscripting (opt=0 or 1)