Re: How to Enable Automatic Recalculation

*To*: mathgroup at smc.vnet.net*Subject*: [mg109860] Re: How to Enable Automatic Recalculation*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Wed, 19 May 2010 20:17:03 -0400 (EDT)

There IS a "simple" answer. Actually, two answers. it used to be that the only way to do this was to use SetDelayed ( := ) for the symbol you wanted to be recalculated whenever you changed another variable whose values was specified by Set ( = ). Since Mathematica 6, you also have the more sophisticated method of using Dynamic quantities. (* method 1: use SetDelayed instead of Set for b *) a = 5; b := 3 + a b 8 a = Pi; b 3 + Pi (* method 2: use Dynamic *) Clear[a,b] Dynamic[a] a a = 3; (* preceding output changes to 3 *) b = 3 + a 6 a = Pi; b 3 + Pi (* method 3: another way to use Dynamic *) Clear[a,b] a = 3; Dynamic[b = 3 + a] 6 a = Pi; (* preceding ouptput changes to 3 + Pi *) b 3 + Pi On 5/19/2010 7:01 AM, Victor Roberts wrote: > I'm new to Mathematica, so perhaps there is a simple answer > to this question. > > How to I set Mathematica so that when I change the value > assigned to a variable it will automatically change all > later calculations that use that variable. > > For example, if I set > > a = 5 > > and > > b = 3 + a > > I would like the value of b updated each time I change the > value of a. > > Right how, I need to recalculate each and every expression > that uses the variable a if I change its value. There must > be a better way. > > > -- > Vic Roberts > Replace xxx with vdr in e-mail address. > -- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2859 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305