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May
7
comment How to stop optimization (e.g. NMinimize) after reaching target value
FindInstance[f[x, y] <= -5, {x, y}]?
May
6
comment Build an InterpolatingFunction with ElementMeshInterpolation
I guess you could build a list of 2D interpolating functions using ElementMeshInterpolation, and then interpolate between their values in t?
May
5
revised Solving a system of ode and plotting the nullclines
added 107 characters in body
May
5
comment Removing solutions which are particular cases of others
Do you also know for each solution what the free variables (C[1], C[2], etc.) are?
May
1
comment ParametricPlot3D of Boy's surface
You could also add the option RegionFunction -> Function[{x, y, z, u, v}, u^2 + v^2 <= 1] instead of changing the function.
May
1
comment ParametricPlot3D of Boy's surface
Your first problem is that vI is a different variable name; you need v I with a space in between.
Apr
27
comment How to compute and plot an intersection?
Also related: Plotting implicitly-defined space curves
Apr
26
comment How do I plot an expression in mathematica?
Plot expects real-valued functions only. What sort of plot do you want to draw for a complex-valued function?
Apr
25
comment Output an Expression in terms of GoldenRatio
I wonder if Simplify's ComplexityFunction option can be useful here?
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.