RE: Re: Precision of output
- To: mathgroup at smc.vnet.net
- Subject: [mg48242] RE: [mg48209] Re: Precision of output
- From: "DrBob" <drbob at bigfoot.com>
- Date: Wed, 19 May 2004 02:42:22 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
x=N[4209/0.14,100] Precision@x 30064.28571 MachinePrecision The output is machine precision, and hence is formatted to 6 digits by default. Use NumberForm to see more digits. NumberForm[x,20] 30064.28571428572 We have only Machine precision, despite using N[#,100]&, because 0.14 is machine precision (NOT 2-digit precision). N is having no effect at all, because it's being asked for more precision in the output than in the input. SetPrecision can be used for that. You're getting extra precision that's actually meaningless, of course. NumberForm[4209/0.14,20] 4209/0.14//Precision 30064.28571428572 MachinePrecision SetPrecision[4209/0.14,100] 30064.2857142857137660030275583267211914062500000000000000000000000000000000 00\ 00000000000000000000000 DrBob www.eclecticdreams.net -----Original Message----- From: Kazimir [mailto:kazimir04 at yahoo.co.uk] To: mathgroup at smc.vnet.net Subject: [mg48242] [mg48209] Re: Precision of output > N[4209/0.14,100] I get: > 30064.3 Mathematica thinks that only the first two digits are precise and knows nothing about the consecutive digits. In other words it's a standor notation for any number between 0.13500000(continue) and 0.1449999999(continue). Thus, it can not suppose that it will find a preciser answer. To get the desired answer you have to ask N[4209/SetPrecision[0.14, ∞], 100] or 4209/(0.14``100) In the latest case you say that 0.14 is defined with 100 digits and it finds the result with this precision > But if I write N[420900/14,100] I get: > 30064.285714285714285714285714285714285714285714285714285714285714285714 > 285714\ > 28571428571428571428571 Here, you don't put a digital point for 14, thus MATHEMATICA is sure that 14 is 14, and not 13.85 or 14.45 sumthing else, and it finds 100 points. If you add only a digital point like this N[420900/14., 100] you will have the first result. Vlad