Rahul Narain

1,942 reputation

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	1,942 reputation	bio	website		visits	member for	1 year, 3 months
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Dec 29	comment	How to get zeroth-order (piecewise constant) interpolation of scattered data? Oh sweet, that was easy! I don't really need a plot, so this is good enough for me.
Dec 29	comment	How to visualize 3D fit @jenson: I think that's what exactly what whuber meant by plotting in "the $xy$ plane... You don't even need the third dimension." 2D is nice because you don't have to deal with things like occlusions and foreshortening that could obscure the data. I'm reminded of whuber's remarkably simple but illuminating graphic showing the vote counts of the moderator election.
Dec 29	asked	How to get zeroth-order (piecewise constant) interpolation of scattered data?
Dec 29	comment	Image Processing: Finding Orientation and Position of Symmetry Axes This question feels underspecified.
Dec 29	awarded	Quorum
Dec 28	comment	How can I recreate Trott's Riemann Surface plot in Mathematica? I think you're missing an argument. It should be `Function[{x, y, z, r, φ}, ...]`.
Dec 28	comment	How to visualize 3D fit @jenson: Please have a look at my edited answer.
Dec 28	revised	How to visualize 3D fit added 1101 characters in body
Dec 28	awarded	Nice Answer
Dec 28	comment	How to visualize 3D fit I think I misunderstood your comment. @chris seems to have taken care of it though. :)
Dec 28	revised	How to visualize 3D fit added 162 characters in body
Dec 28	answered	How to visualize 3D fit
Dec 27	comment	Define Log so that negative reals evaluate on lower edge of branch Sorry, the branch is actually along $z=-re^{i\theta(r)}$.
Dec 27	comment	Define Log so that negative reals evaluate on lower edge of branch @ssch: Well, inspired by whuber's answer, here's a `Log` with a branch cut along any curve of the form $z = re^{i\theta(r)}$: `branchLog[z_, \[Theta]_] := With[{r = Abs[z]}, Log[z/Exp[I \[Theta][r]]] + I \[Theta][r]]`. Then for `ArcTan` you can do `ExpToTrig[TrigToExp@ArcTan[z] /. Log[z_] -> branchLog[z, \[Theta]]]`...
Dec 26	comment	Define Log so that negative reals evaluate on lower edge of branch "What you are asking to do is not the correct math way." They're just taking a slightly different branch cut from the usual one; it's hardly incorrect. There can be more than one right way in mathematics! :)
Dec 26	comment	How do I identify each surface in a multi-surface Plot3D? It's in the documentation, isn't it? "Provide separate styles for different surfaces: `PlotStyle -> {Red, Blue}`". You'll want to provide three colours, get rid of `ColorFunction`, and use `Lighting -> "Neutral"`.
Dec 26	comment	Grid without lines, but with dots You could replace the extra dots with spaces, by inserting this between Transpose and Grid: `MapIndexed[If[OddQ@Total@#2, " ", #1] &, #, {2}] &`
Dec 23	comment	Dynamic Graph visualization Having looked through the options in the GraphPlot documentation, my guess is that what you want is only possible if you write your own force-directed graph layout routine and animate the vertices yourself. In my comments below I was just trying to suggest how to get as close as possible to a nice result with only the existing GraphPlot functionality.
Dec 23	awarded	Critic
Dec 23	comment	Time-series decomposition in Mathematica Well, I went ahead and found the documentation: stat.ethz.ch/R-manual/R-devel/library/stats/html/decompose.html. It seems pretty easy to implement: just a bunch of moving averages. The period of seasonality is assumed to be 1 unit (12 data points in this case), so no need for a heavy-duty NonlinearModelFit.