NCL Home > Documentation > Functions > Array manipulators, Variable manipulators

rm_single_dims

Removes (squeezes) singleton (degenerate) dimensions from an array while preserving metadata.

Available in version 6.1.0 and later.

Prototype

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"  ; This library is automatically loaded
                                                             ; from NCL V6.2.0 onward.
                                                             ; No need for user to explicitly load.

	function rm_single_dims (
		x       
	)

Arguments

x

An array of any shape and type.

Return value

A scalar or a multi-dimensional array with singleton dimensions removed. If no singleton dimensions are detected the return array is identical to the input array.

Description

Returns an array with the same elements as the input array, x, but with singleton dimensions removed. Coordinates associated with singleton dimensions are returned as attributes of the returned array. Hence, no information is lost.

Note: This is analogous to Matlab's squeeze function.

Examples

Example 1

Consider an array dimensioned (2,1,5,1), specifically:

     Variable: x  
     Type: float
     Total Size: 40 bytes
                 10 values
     Number of Dimensions: 4
     Dimensions and sizes:   [time | 2] x [lev | 1] x [lat | 5] x [lon | 1]
     Coordinates: 
                 time: [1..2]
                 lev: [1000..1000]
                 lat: [-90..90]
                 lon: [177.5..177.5]
     Number Of Attributes: 2
       long_name :   foo
       units :       whatever 

 xnew = rm_single_dims(x)
 printVarSummary(xnew)

     Variable: xnew
     Type: float
     Total Size: 40 bytes
                 10 values
     Number of Dimensions: 2
     Dimensions and sizes:   [time | 2] x [lat | 5]
     Coordinates: 
                 time: [1..2]
                 lat: [-90..90]
     Number Of Attributes: 4
       lev : 1000          <== singleton coordinate added as attribute
       lon : 177.5         <== singleton coordinate added as attribute
       long_name :   foo
       units :       whatever  

NOTE: If the location of the singleton dimensions are known by the user a priori, then simple NCL indexing will result in exactly the same result.

 xncl = x(:,0,:,0)
 printVarSummary(xncl)      ; same as xnew above

This is sometimes called "dimension reduction" or "rank reduction".

Contact the Webmaster