source: trunk/SRC/ToBeReviewed/STRING/strsci.pro

;+
;
; @file_comments
; Given a number, returns a string of that B
; number in scientific notation format ( e.g. A x 10^B )
;
; @categories
; String
;
; @param DATA {in}{required}
; A floating point or integer number to be
; converted into a power of 10.
;
; @keyword FORMAT {default='(f12.2)'}
; The format specification used in the string
; conversion for the mantissa (i.e. the
; "A" of "A x 10^B").
;
; @keyword POT_ONLY
; Will return only the "power of 10" part of the
; string (i.e. the "10^B").  Default is to return
; the entire string (e.g. "A x 10^B" )
;
; @keyword MANTISSA_ONLY
; return only mantissa of the string
;
; @keyword SHORT
; return 10^0 as '1' and 10^1 as '10'
;
; @keyword TRIM
; don't insert blanks (i.e. return Ax10^B)
;
; @restrictions
; This function does not "evaluate" the format statement thoroughly
; which can result in somewhat quirky strings. Example:
; print,strsci(-9.999) results in -10.0x10^0 instead of -1.0x10^1.
;
; Need a better symbol than the 'x' for the multiplier...
;
; @examples
;
;   IDL> Result = STRSCI( 2000000, format='(i1)' )
;   IDL> print, result
;   2 x 10!u6!n
;
; which gets plotted as 2 x 10
;
;   IDL> Result = STRSCI( -0.0001 )
;   IDL> print, result
;   -1.00 x 10!u-4!n
;
; which gets plotted as 1.00 x 10
;
;   IDL> Result = STRSCI( 0d0, format='(f13.8)' )
;   IDL> print, result
;   0.00000000
;
; @history
;        bmy, 28 May 1998: VERSION 1.00            B
;           - now returns string of the form A x 10
;        mgs, 29 May 1998:
;           - bug fix: now allows negative numbers
;           - keyword MANTISSA_ONLY added
;           - default format changed to f12.2
;        bmy, 02 Jun 1998:
;           - renamed to STRSCI ("STRing SCIentific notation"),
;        mgs, 03 Jun 1998:
;           - added TRIM keyword
;        mgs, 22 Sep 1998:
;           - added SHORT keyword
;           - modified handling of TRIM keyword
;        mgs, 24 Sep 1998:
;           - bug fix with SHORT flag
;        bmy & mgs, 02 Jun 1999:
;           - now can handle DATA=0.0 correctly
;           - updated comments
;        mgs, 03 Jun 1999:
;           - can now also handle values lt 1 ;-)
;           - and doesn't choke on arrays
;
; @version
; $Id$
;
; Copyright (C) 1998, 1999 Bob Yantosca and Martin Schultz,
; Harvard University
; This software is provided as is without any warranty
; whatsoever. It may be freely used, copied or distributed
; for non-commercial purposes. This copyright notice must be
; kept with any copy of this software. If this software shall
; be used commercially or sold as part of a larger package,
; please contact the author to arrange payment.
; Bugs and comments should be directed to bmy\@io.harvard.edu
; or mgs\@io.harvard.edu with subject "IDL routine strsci"
;-
FUNCTION strsci, data, FORMAT=format, POT_ONLY=pot_only, $
             MANTISSA_ONLY=mantissa_only, SHORT=short, TRIM=trim
;
  compile_opt idl2, strictarrsubs
;

   ;====================================================================
   ; Error checking / Keyword settings
   ;====================================================================
   ;on_error, 2

   if ( n_elements( Data ) eq 0 ) then begin
      return, ''
   endif

   if ( not Keyword_Set( Format ) ) then Format   = '(f12.2)'

   POT_Only      = keyword_set( POT_Only      )
   MANTISSA_Only = keyword_set( MANTISSA_Only )
   Short         = Keyword_Set( Short         )
   Trim          = Keyword_Set( Trim          )

   NDat = n_elements(Data)
   Result = strarr(NDat)

   for i=0,NDat-1 do begin
      ;====================================================================
      ; If ABS( DATA ) > 0 then we can proceed to take the common log.
      ; For DATA < 0, place a "-" sign in front of the number
      ;====================================================================
      if ( Abs( Data[i] ) ne 0.0 ) then begin

         ; take the common log and store in LOG10DATA
         Log10Data = ALog10( Abs( Data[i] ) )

         ; Boolean flag if data < 0
         sign = ( Data[i] lt 0.0 )

         ; Compute the characteristic (int part)
         ; Add the 1d-6 to prevent roundoff errors
         Characteristic = Fix( Log10Data + 1.0d-6 )
         if (Log10Data lt 0) then $
            Characteristic = Characteristic - 1

         ; Compute the Mantissa (frac part) and take its antilog.
         Mantissa = Log10Data - Characteristic
         Mantissa = 10.0^Mantissa

   ;  print,data[i],log10data,mantissa,characteristic,format='(3f24.14,i8)'

         ; String for the coefficient part,
         ; The coefficient is just antilog of the Mantissa
         ; Add the minus sign if DATA < 0.0
         A = StrTrim( String( Mantissa, Format=Format ), 2 )
         if ( Sign ) then A = '-' + A

         ; String for the power of 10 part
         B = '10!u' + strtrim( string( Characteristic ), 2 ) + '!n'
         if ( Short ) then begin
            if ( Characteristic eq 0 ) then B = '1'
            if ( Characteristic eq 1 ) then B = '10'
         endif

         ; composite string
         Result[i] = A + ' x ' + B
         if ( Short AND B eq '1') then Result[i] = A

      ;====================================================================
      ; If DATA = 0, then we cannot take the common log, so return
      ; zeroes for the result strings.  Use the FORMAT string.
      ;====================================================================
      endif else begin
         A      = String( 0d0, Format=Format )
         B      = A
         Result[i] = A

      endelse

      ;====================================================================
      ; Return result to calling program (depending on keyword settings)
      ; Eliminate blanks if TRIM keyword is set
      ;====================================================================
      if ( POT_Only ) then $
         Result[i] = B
      if ( MANTISSA_Only ) then $
         Result[i] = A
      if ( Trim ) then $
         Result[i] = StrCompress( Result[i], /Remove_All )

   endfor

   if (n_elements(Result) eq 1) then $
      Result = Result[0]

   return, Result

end