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Apr
25
comment How to fit a surface to 3D data in Mathematica?
Thanks for fixing the error! Sorry my question was unclear. I understand the quadratic transformation of the data, what I want to know is why you are working with only the subset of the data that lies on the convex hull. If I construct mod using data instead of chv it works fine and I get a better estimate of the volume.
Apr
25
comment How to fit a surface to 3D data in Mathematica?
I think you forgot the definition of f. Also, why not apply LinearModelFit directly to the data points rather than to the vertices of the convex hull?
Apr
24
comment How to draw a tropical surface?
This is fun! $(x^2-y^2,y^2-z^2+1,z^2-x^2-1)$: i.stack.imgur.com/MBoL0.png
Apr
24
comment How to draw a tropical surface?
Nikita, please see my updated answer. @belisarius, your method produces a blank plot for me. Can you explain what it's supposed to do? I don't usually see RegionPlots with equalities in them...
Apr
24
revised How to draw a tropical surface?
deleted 741 characters in body
Apr
23
awarded  Nice Answer
Apr
23
comment numerically solving
What's the problem with making a function that takes $\lambda$ as an argument and calls FindRoot?
Apr
23
comment Integrating a function over a surface integral
The literal implementation Integrate[1/Norm[Grad[e[x, y, z], {x, y, z}]], {x, y, z} ∈ ImplicitRegion[e[x, y, z] == ϵ, {x, y, z}]] seems to work when $E$ is given analytically, but not when it is an InterpolatingFunction constructed from the data.
Apr
23
comment Integrating a function over a surface integral
If I'm not mistaken, the integral is equal to $\displaystyle\frac{\mathrm d}{\mathrm d\epsilon}\iiint_{E(x,y,z)\le\epsilon}\mathrm dV$, is that right? It might be easier to compute that instead, but I'm not sure.
Apr
23
revised Integrating a function over a surface integral
added 17 characters in body
Apr
23
comment Creating a nonlinear phase portrait
I don't understand what the question is.
Apr
22
comment Something like MinDetect but for saddle points
Related (possible duplicate): Identifying critical points/lines of 2/3D image/cubes
Apr
17
comment How to ensure that Polygon[list] plots a simple polygon?
Some more possible solutions are given in the duplicate question Rebuild a polygon so it doesn't self intersect.
Apr
15
comment Plotting Riemann surface of $\sqrt{z}$ in rectangular coordinates
Sqrt will only give you one branch of the complex square root.
Apr
13
revised How to draw a tropical surface?
added 8 characters in body
Apr
13
revised How to draw a tropical surface?
added 2 characters in body
Apr
13
revised How to draw a tropical surface?
edited tags
Apr
13
answered How to draw a tropical surface?
Mar
26
comment Floating point arithmetic bug caused by Table[]
What Every Computer Scientist Should Know About Floating-Point Arithmetic
Mar
15
revised How can I make a 3D Plot with NDSolve?
added 30 characters in body