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Re: Approximate Zero Times A Symbol

  • To: mathgroup at smc.vnet.net
  • Subject: [mg127122] Re: Approximate Zero Times A Symbol
  • From: Richard Fateman <fateman at eecs.berkeley.edu>
  • Date: Sun, 1 Jul 2012 02:09:54 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <201206270811.EAA18698@smc.vnet.net> <19783652.3140.1340794328091.JavaMail.root@m06> <jsh3a9$sir$1@smc.vnet.net> <18402214.58885.1341077225203.JavaMail.root@m06> <000501cd56f2$cb6cec40$6246c4c0$@comcast.net>

I don't know much about NumberFormat or Sliders, but look at this:

Coefficient[a*x+b*y, {x,y}]     returns {a,b}
Coefficient[    b*y,{ x,y}]     returns {0,b}

I get the feeling that there is something resembling a "thought crime" 
that is causing you
problems.  That is, confusing the "computation of a value"   and the 
"display of some
attributes of a value".  It is not necessary to change the Accuracy or 
Precision of a value
to display it.  It is not necessary for you to make Mathematica to (not) 
simplify 0.0*x to 0.0.
All you have to do is figure out what you want to display, as above.

NumberForm is essentially a way of taking values and computing some 
strings of
characters.  The string for a number has some relation with the actual 
value,
  but  given a result of {0,b}  from Coefficient, presumably you can make
any kind of string you wish, e.g.

      x-coefficient        y-coefficient
  ----------------------------------------
  |.........0........|..........b........|
  ----------------------------------------
RJF



On 6/30/2012 12:01 PM, djmpark wrote:
> Thanks for your reply Richard.
>
> Basically I was interested in formatting a vector a x + b y to so many
> places and keeping both terms present even when a or b was an approximate
> zero. (My dislike of Dynamic displays that jitter and jump.)
..big snip...



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