Drexel dragonThe Math ForumDonate to the Math Forum



Search All of the Math Forum:

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.


Math Forum » Discussions » Software » comp.soft-sys.math.mathematica

Topic: Differencing two equations
Replies: 7   Last Post: Sep 8, 2013 2:56 AM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
Alexei Boulbitch

Posts: 483
Registered: 2/28/08
Re: Differencing two equations
Posted: Feb 13, 2013 4:48 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

Dear community,

I have seen in this thread a lot of nice approaches that I really admire, but
writing simply:

eq2 = b == s;
eq1 = a == r;

eq1[[1]] - eq2[[1]] == eq1[[2]] - eq2[[2]]

a - b == r - s

is shorter.

Have fun, Alexei



> a==r
> b==s


> I'd like to get:
> a-b == r-s


Hi. Here are a few ideas.

v={a==r,b==s};

Equal@@Subtract@@@{v[[All,1]],v[[All,-1]]}
a-b==r-s

Equal@@Subtract@@@Transpose[List@@@v]
a-b==r-s

{* I like Inner *)

Inner[Subtract,a==r,b==s,Equal]
a-b==r-s

// or...

Inner[Subtract,v[[1]],v[[2]],Equal]
a-b==r-s


= = = = = = = = = =
HTH :>)
=E2=80=A8Dana DeLouis
Mac & Mathematica 9
=E2=80=A8= = = = = = = = = =





On Sunday, February 10, 2013 3:35:06 AM UTC-5, G B wrote:
> I'm brand new to Mathematica, so I apologize for the naive questions...
>
>
>
> I'm trying to figure out how to difference two equations. Basically if I=

have:
>
> a==r
>
> b==s
>
>
>
> I'd like to get:
>
> a-b == r-s
>
>
>
> What I'm getting is more like (a==r) - (b==s). I'm not sure how that's a useful result, but is there a function to do what I'm looking for?
>
>
>
> A quick search of the archives seem to bring up ways of doing this from using transformation rules to swap heads to unlocking the Equals operator and hacking its behavior. I'd like to avoid doing that kind of rewiring for a simple operation, and I'd like to keep the syntax clean.
>
>
>
> The Core Language documentation makes a big point of how everything is basically a list with different heads. In this case, what I'm trying to do would work if it were treated as a list ({a,b}-{r,s} returns {a-b,r-s}) but doesn't work under Equal.
>
>
>
> Thanks for any suggestions.




Alexei BOULBITCH, Dr., habil.
IEE S.A.
ZAE Weiergewan,
11, rue Edmond Reuter,
L-5326 Contern, LUXEMBOURG

Office phone : +352-2454-2566
Office fax: +352-2454-3566
mobile phone: +49 151 52 40 66 44

e-mail: alexei.boulbitch@iee.lu







Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© Drexel University 1994-2014. All Rights Reserved.
The Math Forum is a research and educational enterprise of the Drexel University School of Education.