[Date Index]
[Thread Index]
[Author Index]
Avoid long output, Real variables?
*To*: mathgroup at smc.vnet.net
*Subject*: [mg20424] Avoid long output, Real variables?
*From*: bergervo at prl.philips.nl (Bergervoet J.R.M.)
*Date*: Tue, 26 Oct 1999 00:33:08 -0400
*Organization*: Philips Research Laboratories Eindhoven, Netherlands
*Sender*: owner-wri-mathgroup at wolfram.com
Is it possible to tell Mathematica that a variable, x, is Real?
I am looking for commands like those of some competing vendor:
assume(x, real)
assume(x>0)
If I cannot declare x to be Real, I get clumsy answers. For
instance, a Fourier transform which for real x is just:
2 BesselK[0, x Sign[x]]
gives me instead a pretty long answer where the actual solution
for real x is hardly recognizable between the rest:
In[4]:=Integrate[E^(I*k*x)/Sqrt[1+k^2]/(2*Pi), {k,-Infinity,Infinity}]
Out[4]= If[Im[x] == 0, 2 BesselK[0, x Sign[x]],
I k x
E
Integrate[------------, {k, -Infinity, Infinity}]] / (2 Pi)
2
Sqrt[1 + k ]
In[5]:=
And it can get worse if several variables are involved. So I really
hope that someone can teach me how to declare them Real (or positive).
Thanks in advance,
Jos
Prev by Date:
**Re: OOP in Mathematica -- please help a newbie**
Next by Date:
**Re: Display problems**
Previous by thread:
**Re: Mathematica for Macintosh Plus i.e. 68000 processors?**
Next by thread:
**Re: Avoid long output, Real variables?**
| |