Lost news postings

• To: mathgroup at smc.vnet.net
• Subject: [mg66078] Lost news postings
• From: "Steve Luttrell" <steve at luttrell.org.uk>
• Date: Fri, 28 Apr 2006 06:33:39 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```I have noticed that my postings to MathGroup are no longer appearing. For
instance, the following one sent recently has not appeared:

Re: Setting up equations

Reduce[ForAll[{x,y,z},5 x+6 y+7 z==a x+b y+c z]]

Steve Luttrell

"Yaroslav Bulatov" < <mailto:yaroslavvb at gmail.com> yaroslavvb at gmail.com>
wrote in message
<news:e2nd3i\$33m\$1 at smc.vnet.net> news:e2nd3i\$33m\$1 at smc.vnet.net...
> I'm trying to do things of the form
> Solve[5 x + 6 y + 7 z == a x + b y + c z, {a, b, c}]
>
> But since x,y,z are variables, what I really mean is
> Solve[5==a && 6==b && 7==c], so I need to convert to this form
>
> If I only have one variable, the following does what I need
>
> LogicalExpand[a*x + b*x^2 + O[x]^3 == 2*x + 3*x^2 + O[x]^3]
>
> But what to do if I have several variables?
>

and this one sent several days ago has not appeared

Re: A bug in ListPlot3D ?

The Help browser says:

ListPlot3D[array] generates a three\[Hyphen]dimensional plot of a
surface representing an array of height values.

array should be a rectangular array of real numbers, representing z
values. There will be holes in the surface corresponding to any array
elements that are not real numbers.

However, this is not the way in which you have used ListPlot3D.

You should create an interpolatin function and then plot that.

f=Interpolation[{{3,55,-3},{3,60,-3},{4,55,-2},{4,60,-2.5}}];
Plot3D[f[x,y],{x,3,4},{y,55,60}];

Steve Luttrell

"Hui Fang" < <mailto:fangh73 at xmu.edu.cn> fangh73 at xmu.edu.cn> wrote in
message
<news:e2crce\$k1p\$1 at smc.vnet.net> news:e2crce\$k1p\$1 at smc.vnet.net...
> I'm trying to use ListPlot3D to show a interesting surface. However, the
> result is very confusing. Since my data is rather long, I'll just use 4
> points to explain what happened.
>
>
>
> ListPlot3D[{{3,55,-3},{3,60,-3},{4,55,-2},{4,60,-2.5}}]
>
>
>
> The range of x and y axes are between {1,3} and {1,4} respectively, but
> the
> y axes is supposed to be about 60! The worse thing is the z axis has a
> range
> from 1 to 60, not showing anything NEGATIVE!
>
>
>
> Anybody has any idea what's going on? I am using Mathematica 4.1. Thanks a
> lot!
>
>
>
> Dr. H. Fang
>
> Department of Physics
>
> Xiamen Univeristy
>
> Xiamen, Fujian 361005
>
>

I recall you mentioning that there had been problems with your spam filter.
Perhaps I am being redirected into the trash.

Steve Luttrell
West Malvern, UK

```

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