;+ ; NAME: ; SIGFIG ; ; ; PURPOSE: ; Accept a scalar numerical value or an array of numbers and ; return the numbers as strings with the specified number of ; significant figures. ; ; CALLING SEQUENCE: ; RESULT = SigFig(Number, Nfig [, /SCIENTIFIC, /PLUSSES, /NUMERICAL) ; ; INPUTS: ; Number - Scalar or array of numerical values (float, double, int) ; Nfig - Number of signficant figures desired in the output ; ; OUTPUTS: ; String representation of the input with the specified number ; of signficant figures. ; ; KEYWORD PARAMTERS: ; /SCIENTIFIC - return the numbers in scientific notation ; /PLUSSES - Include plus signs for positive numbers ; /NUMERICAL - Return numerical, rather than string, values ; ; EXAMPLE: ; IDL> print, sigfig(-0.0001234, 2) ; -0.00012 ; IDL> print, sigfig(1.234, 1) ; 1. ; IDL> print, sigfig(1234, 1) ; 1000 ; IDL> print, sigfig(-0.0001234, 2, /sci) ; -1.2e-4 ; IDL> print, sigfig(1234, 2, /plus) ; +1200 ; IDL> print, sigfig(1234, 2, /plus, /sci) ; +1.2e+3 ; ; MODIFICATION HISTORY: ; Inspired long ago by Erik Rosolowsky's SIGFIG: ; http://www.cfa.harvard.edu/~erosolow/idl/lib/lib.html#SIGFIG ; ; This version written by JohnJohn Sept 29, 2005 ; ; 24 Oct 2007 - If result is a single number, return scalar value ; instead of an 1-element array. Thanks Mike Liu. ; 2 Apr 2008 - Fixed 1-element array issue, but for real this time. ;- ;;; SF_STR - The way STRING() should behave by default function sf_str, stringin, format=format return, strcompress(string(stringin, format=format), /rem) end ;;; SF_TRANS_DEC - TRANSlate the DECimal point in a number of order ;;; unity, round it, and translate back. function sf_trans_dec, numin, nsigin, order_inc=order_inc nel = n_elements(numin) ;;; Double precision can't handle more than 19 sig figs nsig = nsigin < 19 ;;; Gonna have to move the decimal nsig-1 places to the right before rounding move = nsig-1 len = max(strlen(numin)) move = move < (len-1) ;;; Create a string with just the digits, no decimal nodec = strmid(numin, 0, 1)+strmid(numin, 2, len) ;;; Move the decimal, so nsig digits are to the left of the new ;;; decimal position num0 = strmid(nodec,0,1+move)+'.'+strmid(nodec,1+move,len) ;;; Round the new number num1 = sf_str(round(double(num0),/l64)) len1 = strlen(num1) ;;; If the number increases an order of magnitude after rounding, set ;;; order_inc=1 so the calling routine knows to add one to the order ;;; of magnitude order_inc = len1 gt nsig ;;; Move the decimal back and return to sender num = strmid(num1, 0, 1)+'.'+strmid(num1, 1, nsig-1) return, num end function sigfig, NumIn, Nfig \$ , string_return=string_return \$ , scientific=scientific \$ , numerical=numerical \$ , plusses=plusses Num = double(NumIn) Nel = n_elements(Num) ;;; Convert the input number to scientific notation TestString = sf_str(abs(double(Num)), format='(e)') Epos = strpos(TestString[0], 'e') ;;; Test sign of the order Osign = intarr(Nel)+1 StrOsign = strmid(TestString, Epos+1, 1) Wneg = where(strosign eq '-', Nneg) if Nneg gt 0 then Osign[Wneg] = -1 ;;; Test sign of numbers, form string of minus signs for negative vals NegSign = strarr(Nel) + (keyword_set(plusses) ? '+' : '') Negative = where(Num lt 0, Nneg) if Nneg gt 0 then NegSign[Negative] = '-' ;;; What are the orders of magnitude of the values? Order = fix(sf_str(strmid(TestString, Epos+2, 2))) ;;; Convert all values to order unity for rounding NumUnit = strmid(TestString,0,epos) ;;; Use TRANS_DEC to round unit values NumTrans = sf_trans_dec(NumUnit, Nfig, order_inc=Order_Inc) Order = order + Osign*order_inc Len = strlen(NumTrans[0]) ;;; Exit early without looping for /NUMERICAL or /SCIENTIFIC if keyword_set(numerical) then begin NumRound = NegSign+NumTrans+'e'+StrOsign+sf_str(Order) if n_elements(NumRound) eq 1 then return, double(NumRound[0]) else \$ return, double(NumRound) endif if keyword_set(scientific) then begin NumRound = NegSign+NumTrans+'e'+StrOsign+sf_str(Order) if n_elements(NumRound) eq 1 then return, NumRound[0] else \$ return, NumRound endif NumRound = strarr(Nel) for i = 0, Nel-1 do begin if Osign[i]*Order[i]+1 gt Nfig then Format = '(I40)' else begin d = sf_str(fix(Nfig-(Osign[i]*Order[i])-1) > 0) Format = '(F40.' + d + ')' endelse New = NumTrans[i] * 10d^(Osign[i] * Order[i]) NumRound[i] = NegSign[i]+sf_str(New, format=Format) endfor if n_elements(NumRound) eq 1 then return, NumRound[0] return, NumRound end