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dim_rmvmean_n

Calculates and removes the mean of the given dimension(s) at all other dimensions.

Prototype

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

	return_val [dimsizes(x)] :  float or double

Arguments

A variable of numeric type and any dimensionality.

dims

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

Return value

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

The dimensionality is the same as the input dimensionality.

Description

The dim_rmvmean_n function calculates and removes the mean from all elements of the dimensions indicated by dims for each index of the remaining dimensions. Missing values are ignored.

Use the dim_rmvmean_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 just the deviations from the mean; (b) replace the variable x with the deviations.

  xNew = dim_rmvmean_n(x,0)      ; new variable
  x    = dim_rmvmean_n(x,0)      ; overwrite with deviations

  ; Use dim_rmvmean_n_Wrap if metadata retention is desired
  ; x    = dim_rmvmean_n_Wrap(x,0)      ; overwrite with deviations

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

Example 2:

Let x be a 3-dimensional array with dimension sizes (ntim, nlat, nlon). To remove the means of the "nlon" dimension:

   xRmvLon = dim_rmvmean_n (x,2)       ; new variable containing deviations (no metadata)
   x       = dim_rmvmean_n (x,2)       ; overwrite with deviations

   ; Use dim_rmvmean_n_Wrap if metadata retention is desired 
   ; xRmvLon = dim_rmvmean_n_Wrap(x, 2)
   ; x       = dim_rmvmean_n_Wrap (x,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). To remove the mean of the time dimension from all lat/lon indices:

   xRmvTime = dim_rmvmean_n(x,0)

   ; Use dim_rmvmean_n_Wrap if metadata retention is desired 
   ; xRmvTime = dim_rmvmean_n_Wrap(x,0)

Example 4:

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

   xRmv = dim_rmvmean_n(x,(/0,1/))

   ; Use dim_rmvmean_n_Wrap if metadata retention is desired  
   ; xRmv = dim_rmvmean_n_Wrap(x,(/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). Monthly anomalies for each month could be calculated using array subscripting.