NCL Home > Documentation > Functions > File IO

isfilevar

Checks if specified file variables are defined in a file.

Prototype

	function isfilevar (
		thefile [1] : file,    
		varnames    : string   
	)

	return_val [dimsizes(varnames)] :  logical

Arguments

thefile

reference to a file. It is created using addfile. Thus it must be a supported file format.

varnames

an array of strings of any dimension

Return value

The output is a logical array with the same dimensions as the varnames parameter.

Description

For each element in the varnames parameter, isfilevar returns True if the variable is present on the file referenced by thefile and False if not. If the parameter thefile is not a valid file, then a single missing value is returned.

See Also

isvar

Examples

Example 1: If a variable named X resides in the file referenced by f, read it to memory using:

  f = addfile ("dummy.hdf", "r")
  if (isfilevar(f, "X")) then
    x = f->X
  end if

Example 2: Loop through a series of possible variable names and read the first occurrence of that variable name. Use the NCL break keyword to exit the loop. The '$' character is used to allow string substitution in the variable name:

  rotaName = (/"ANGLE", "angle", "UTAN", "utan", "ROTA", "rota" /)
  do i=0,dimsizes(rotaName)-1
    if (isfilevar(f,rotaName(i))) then
      rot = ndtooned(f->$rotaName(i)$)
      break           ; exit from do loop
    end if
  end do