;+ ; NAME: ; leading_digit ; ; ; PURPOSE: ; return the leading digit of a number. E.g. 1234 -> 1, 0.345 -> 3. ; This is used in the computation of Benford's Law ; (http://en.wikipedia.org/wiki/Benford%27s_law) ; ; ; INPUTS: ; in: number (or array of numbers) to find the leading digit of ; ; ; OUTPUTS: ; the leading digit of the number ; ; ; EXAMPLE: ; IDL> print, leading_digit([0.0034, 6123, 0, -0.12343]) ; 3 6 0 1 ; ; ; MODIFICATION HISTORY: ; ; Mon Jun 16 16:36:17 2008, Brian Larsen ; ; written and tested ; ;- FUNCTION leading_digit, in compile_opt strictarr in2 = trim(string(abs(in), format = '(e)')) ans = strmid(in2,0, 1) RETURN, ans END