FUNCTION WHERENAN, ARRAY, COUNT ;+ ; NAME: ; WHERENAN() ; PURPOSE: ; Find the indices of all big-endian NaN values in an array. OBSOLETE ; EXPLANATION: ; Find the positions of all values within an array that correspond to the ; big-endian NaN (not-a-number) special values. ; ; THIS PROCEDURE ONLY IDENTIFIES BIG_ENDIAN NaN VALUES. DO NOT USE IT ; TO IDENTIFY NaN VALUES IN GENERAL. Instead, to identify NaN values on ; the host machine use the FINITE() function ; ; IDL> result = where( finite(array,/NAN) ) ; ; The main purpose of this routine is to catch NaN special values ; written in big_endian format (e.g. FITS data) on a little endian ; machine prior to conversion with e.g. IEEE_TO_HOST. It was needed ; many years ago because VMS machines could not handle big-endian ; special values, but this routine is now kept only for backwards ; compatibility. ; ; CALLING SEQUENCE: ; Result = WHERENAN( ARRAY [, COUNT ] ) ; ; INPUT PARAMETERS: ; ARRAY = Array to test against the IEEE NaN special values. Must be ; of either floating point, double-precision, or complex type. ; ; OUTPUTS: ; The result of the function is the indices of all values of ARRAY ; corresponding to the IEEE NaN specification, similar to the IDL WHERE ; function. ; ; OPTIONAL OUTPUT PARAMETERS: ; COUNT = Number of values found corresponding to IEEE NaN. ; ; SIDE EFFECTS: ; If no NaN values are found, or if ARRAY is not of type float, double ; precision, or complex, then -1 is returned, and COUNT is set to 0. ; ; RESTRICTIONS: ; ARRAY must be of type float, double-precision, or complex. ; ; PROCEDURE: ; The bit patterns of the numbers being tested are compared against the ; IEEE NaN standard. ; ; MODIFICATION HISTORY: ; William Thompson, Feb. 1992. ; William Thompson, Oct. 1992, fixed bug regarding order of bytes on VAX ; machines. ; Converted to IDL V5.0 W. Landsman September 1997 ;- ; ON_ERROR,2 ; ; Check the number of parameters. ; IF N_PARAMS() LT 1 THEN MESSAGE, $ 'Syntax: Result = WHERENAN(ARRAY [,COUNT])' ; ; Parse the input array based on the datatype. ; SZ = SIZE(ARRAY) CASE SZ[SZ[0]+1] OF ; ; Single precision floating point. ; 4: BEGIN LARRAY = LONG(ARRAY,0,N_ELEMENTS(ARRAY)) BYTEORDER,LARRAY,/NTOHL E0 = '7F800000'X E = LARRAY AND E0 F = LARRAY AND '7FFFFF'X RESULT = WHERE((E EQ E0) AND (F NE 0), COUNT) END ; ; Double precision floating point. ; 5: BEGIN LARRAY = LONG(ARRAY,0,2,N_ELEMENTS(ARRAY)) BYTEORDER,LARRAY,/NTOHL E0 = '7FF00000'X E = LARRAY[0,*] AND E0 F1 = LARRAY[0,*] AND 'FFFFF'X RESULT = WHERE((E EQ E0) AND ((F1 NE 0) OR $ (LARRAY[1,*] NE 0)), COUNT) END ; ; Single precision complex floating point. ; 6: BEGIN LARRAY = LONG(ARRAY,0,2,N_ELEMENTS(ARRAY)) BYTEORDER,LARRAY,/NTOHL E0 = '7F800000'X E1 = LARRAY[0,*] AND E0 E2 = LARRAY[1,*] AND E0 F1 = LARRAY[0,*] AND '7FFFFF'X F2 = LARRAY[1,*] AND '7FFFFF'X RESULT = WHERE(((E1 EQ E0) AND (F1 NE 0)) OR $ ((E2 EQ E0) AND (F2 NE 0)), COUNT) END ELSE: BEGIN MESSAGE,'Data type must be floating point',/INFORMATIONAL RESULT = -1 COUNT = 0 END ENDCASE ; RETURN, RESULT END