Re: Turning on numerical computation

*To*: mathgroup at smc.vnet.net*Subject*: [mg63064] Re: Turning on numerical computation*From*: David Bailey <dave at Remove_Thisdbailey.co.uk>*Date*: Tue, 13 Dec 2005 03:40:45 -0500 (EST)*References*: <dmuice$mlr$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

New Guy wrote: > Mathematica outputs answers in symbolic form as the exact answer. > > I can force numeric output by N or using a decimal. > > Can I make numeric answers the default until I want to go back to > symbolic. In other words, can I turn numeric on and off as my default > output? > > Thank you. > Hello, As two people have already pointed out, you CAN use $Post to change the default behaviour of Mathematica. However, I wonder if this is really wise - particularly if, as your name suggests - you are fairly new to Mathematica. Setting $Post=N will do many things - including converting integers to reals, and spoiling any algebraic calculations that you do (unless you like polynomials with fractional coefficients represented as real numbers!). You could make a more complicated assignment to $Post and avoid some of these problems, but even so, the point is, everyone learns Mathematica by using it, and you will learn the 'wrong' system. In any particular situation there is usually a better alternative. Say you are doing a lot of calculations with Log with integer values - these don't usually evaluate because the result is not exact. However, you can always define your own Log function to get round that problem: realLog[x_]:=N[Log[x]] David Bailey http://www.dbaileyconsultancy.co.uk