Re: Transformations in expressions
- To: mathgroup at smc.vnet.net
- Subject: [mg91891] Re: Transformations in expressions
- From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
- Date: Fri, 12 Sep 2008 05:25:47 -0400 (EDT)
- Organization: The Open University, Milton Keynes, UK
- References: <gaar3o$16q$1@smc.vnet.net>
Miguel wrote:
> How can I to transform a specific expression to other by substitution
> of a part of it.
>
> For example, I want to transform the expression Log[x^2+y^3]/
> Sin[x^2+y^3] in Log[z]/Sin[z] by substitution x^2+y^3 --> z.
You could write a transformation rule ("->") and apply it thanks to the
replacement operator ("/.")
In[1]:= expr = Log[x^2 + y^3]/Sin[x^2 + y^3] ;
expr /. x^2 + y^3 -> z
Out[2]= Csc[z] Log[z]
> And other question: Is the new expression dependent of z. I see it is,
> but how can I to programar it.
In[3]:= f[z_] = Log[x^2 + y^3]/Sin[x^2 + y^3] /. x^2 + y^3 -> z
f[2]
% // N
Out[3]= Csc[z] Log[z]
Out[4]= Csc[2] Log[2]
Out[5]= 0.762289
You should have a look at
tutorial/DefiningFunctions
http://reference.wolfram.com/mathematica/tutorial/DefiningFunctions.html
Regards,
-- Jean-Marc