formatting text with E-XX

kommesel has asked for the wisdom of the Perl Monks concerning the following question:

hello, my question is this: Suppose I have a number: 1.567E-09 I want to round it to two decimal points, but to keep the scale: i.e 1.57E-09 How do I do it without writing a whole subroutine? I tried to use sprintf "%.2f" , but it simply rounded it to 0, which is not what I had in mind. Thanks, and to those who had their Johnson partially severed when they were 8 days old, Hatima Tova.

Comment on formatting text with E-XX

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Re: formatting text with E-XX by shenme (Priest) on Oct 01, 2003 at 12:19 UTC
What about using something like '%8.3g', just like with C ? Or even '%8.3G' if you really want the uppercase 'E'. perl -e "$f=1.567E-09;printf qq{ '%s' is '%8.3g'$/}, $f, $f;" '1.567e-009' is '1.57e-009' perl -e "$f=1.567E-09;printf qq{ '%s' is '%8.3G'$/}, $f, $f;" '1.567e-009' is '1.57E-009' If you need to force only two digits on the exponent you might have to resort to an RE?	[reply]
Re: formatting text with E-XX by rinceWind (Monsignor) on Oct 01, 2003 at 12:30 UTC
I think you want sprintf "%1.2E" which will force scientific notation. From perldoc -f sprintf: `%e a floating-point number, in scientific notation %f a floating-point number, in fixed decimal notation %g a floating-point number, in %e or %f notation ... %E like %e, but using an upper-case "E"` [download] Hope this helps -- I'm Not Just Another Perl Hacker	[reply] [d/l]
Re: formatting text with E-XX by robartes (Priest) on Oct 01, 2003 at 12:30 UTC
`$ perl -e 'printf("%.3G","1.567E-09")' 1.57E-09` [download] CU Robartes-	[reply] [d/l]
Re: formatting text with E-XX by ambrus (Abbot) on Oct 01, 2003 at 13:37 UTC
You have to use %g instead of %f. The difference between these is that %f never uses "e", %e always uses it, %g decides from the magnitude of numbers. So, `printf "%.3g\n",1.567E-09;` works. You need `".3g"` instead of `".2"` because there are 3 digits together with the one before the point.	[reply] [d/l] [select]