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conform_dims

Expands an array or scalar so that it conforms to the shape of the given dimension sizes.

Prototype

	function conform_dims (
		dims  : byte, short, integer or long,  
		r     ,                                
		ndim  : integer                        
	)

	return_val [dims] :  typeof(r)

Arguments

dims

An array of dimension sizes of which r will be conformed to.

r

A scalar or an array whose dimensions must be a subset of dims.

ndim

An array of dimension indexes to indicate which dimension sizes indicated by dims match the dimensions in r. Dimension numbering starts at the left and must be increasing. The leftmost dimension index is 0, the next dimension index is 1, and so on. If r is a scalar, then ndim can have the special value of -1 (see below).

As of version 6.4.0, ndim can contain dimension indexes who sizes in r reference degenerate dimensions. The degenerate dimensions will be automatically expanded to the corresponding dimension size indicated by dims (see below).

Description

This function will create a new variable that has dimensions dims and the same type as r. The values of r will be copied to all of the other dimensions.

If r is a scalar and ndim is -1, then the scalar value will be copied to all elements of a new array of the same size as indicated by dims.

One use of this function is to create a new (and often temporary) variable so that it can be used for something like multiplication between two variables.

This function is identical to conform, except you pass in the dimension sizes of the new array size that you want to conform to, rather than the array itself. This method is preferable because you don't need to create the array before using this function.

See Also

conform, reshape, reshape_ind

Examples

For more examples, see the conform examples section.

Example 1

This is a simple example to show how conform_dims works. Take a 1D array with the values (/1,2,3,4,5/), and "conform" it to a 3 x 5 array, and then a 5 x 3 array:

   x = (/1,2,3,4,5/)
   xc1 = conform_dims((/3,5/),x,1)
   xc2 = conform_dims((/5,3/),x,0)

  fmt1 = "5i3"
  fmt2 = "3i3"
  write_matrix (xc1, fmt1, False)
  write_matrix (xc2, fmt2, False)
Output:

  1  2  3  4  5
  1  2  3  4  5
  1  2  3  4  5
  
  1  1  1
  2  2  2
  3  3  3
  4  4  4
  5  5  5
Example 2

If you have a 3D array x with sizes ntim x nlat x mlon and an array t of length ntim, then the following line:

    tConform = conform_dims (dimsizes(x),t,0) 

will yield an array tConform that is dimensioned ntim x nlat x mlon where the contents of t are propagated to all dimensions of x.

Example 3

Assume T is a 4D array with dimensions ntim x klev x nlat x mlon and dp is an array of length klev. If you want to compute the column pressure weighted mean temperature at all times, then use:

  dpC = conform_dims(dimsizes(T), dp, 1)  ; => (ntim,klev,nlat,mlon)
  T_wgtAve = dim_sum(T*dpC)/dim_sum(dpC)

Example 4

Assume ntim1=100 and ntim2=1, and that T1 is a 4D array with dimensions ntim1 x klev x nlat x mlon and dp is an array with dimensions ntim2 x klev. Note that ntim2 is a degenerate dimension.

In NCL V6.3.0 and earlier, if you want to conform dp to the same size of T1, you must first subscript dp to collapse the degenerate dimension:

  dpC = conform_dims(dimsizes(T), dp(0,:), 1)   ; => (ntim1,klev,nlat,mlon)

In NCL V6.3.0 and later, you don't need to collapse the degenerate dimension:

  dpC = conform_dims(dimsizes(T), dp, (/0,1/))  ; => (ntim1,klev,nlat,mlon)