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dim_median_n

Computes the median of a variable's given dimensions at all other dimensions.

Available in version 5.1.1 and later.

Prototype

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

	return_val  :  float or double

Arguments

A variable of numeric type and any dimensionality.

dims

The dimension(s) of x on which to determine the median. Must be consecutive and monotonically increasing.

Return value

The output will be double if x is double, and float otherwise.

The output dimensionality will be the same as all but dims's dimensions of the input variable. The dimension rank of the input variable will be reduced by the rank of dims.

Description

The dim_median_n function determines the median of all elements in the dimensions indicated by dims for each index of the remaining dimensions. Missing values are ignored.

The median is a robust estimate of the mean.

Examples

Example 1

Let x be a 1-dimensional array, then:

   xMed = dim_median_n(x,0)   ; xMed is a scalar

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

Example 2

Create a variable (q) of size (3,5,10) array. Then calculate the median of the rightmost dimension.

    q    = random_uniform(-20,100,(/3,5,10/))
    qMed = dim_median_n(q,2)   ;==>  qMed(3,5)

Example 3

Let x be of size (ntim,nlat,mlon) and with named dimensions "time", "lat" and "lon", respectively. Then, for each time and latitude, the median longitude value may be obtained via:

    xMedLon = dim_median_n(x,2)    ; ==> xMedLon(ntim,nlat)

Example 4

Let x be defined as in Example 3: x(time,lat,lon). Determine the median value over all time at each latitude/longitude grid point.

    xMedTime = dim_median_n(x, 0)    ; ==> xMedTime(nlat,nlon)

Example 5

Let x x(time,level,lat,lon). Determine the median value over all lat/lon at each time/level grid point.