Wolfram Mathematica

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7:33 AM

@yode Doesn't look right ... Can you send me the graph so I don't have to retype the whole thing?

@yode OK, I re-typed it and reproduced the problem. Feel free to file a bug next time, even if you are not absolutely sure that it is a bug.

@yode As a workaround, try IGFeedbackArcSet[g, Method -> "EadesLinSmyth"].

Szabolcs

8:15 AM

@yode Open IGraphM.m and find the definition of IGFeedbackArcSet. On the first line (in the Block) change igMakeFastWeighted to igMake. This will fix the problem. The workaround I mentioned above is not good, that method will also return wrong results sometimes without this fix.

Kuba

Q: How useful is $EvaluationEnvironment?

$EvaluationEnvironment was supposed to be a panacea for: Good way to discriminate between Mathematica/PlayerPro/CDFPlayer But from my experience it is not working fully in "desktop" area. The questions are: are my "not working" and "working" tests done properly? don't have time to check every...

evaluation

Szabolcs

and you know I did have tests for this function ...

Kuba

@Szabolcs me?

Szabolcs

9:10 AM

@Kuba No, sorry, was talking to yode

2 hours later…

Kuba

10:50 AM

@Pickett are you aware of a quick way to convert

<|"a" -> Identity, "b" -> True|> to

"{
\"a\": \"Identity\",
\"b\": true
}"

ExportString[#, "RawJSON"]& can't handle unknown expressions like Identity

user3183724

A bit of a stupid question, but I'm having some trouble visualizing the features of a certain contour plot. The thing is that the data ranges from about 0.99 to 0.91, but that most of the features that I am interested in are in the 0.99-0.98 range. If I use a linear scale these features wash out completely, so I suppose I should use something more like a logarithmic type of scaling, but rescaled to the upper and lower bounds. Is that simple to do? I can't think of how fro mthe top of my head

yode

11:44 AM

@Szabolcs Sorry,I'm in sleep.I had thought you have seen the graph talked in recently.:)

Karsten 7.

Q: How can I make a density plot (or contour plot) with an arbitrary nonlinear scale (e.g. arcsinh, log, biexponential)?

I was inspired by this question, which showed how we can apply logarithmic scaling to a density plot. But I'm not always a fan of a logarithmic scale - it tends to overemphasize smaller features. Consider the example from the post linked above, $\mathrm{sinc}(x)^2$. Here is a comparison of li...

plotting visualization

@Kuba You didn't ask me and I'm not sure this is the kind of solution you are looking for, but

ExportString[<|"a" -> Identity, "b" -> True|> /. Identity :> "Identity", "RawJSON"]

does work.

Kuba

12:02 PM

@Karsten7. I think OP about scaling x and y rather than z.

@Karsten7. Thanks, but the question is more general. Something like /. p:Except[True|False] :> ToString[p] but I'm not sure if there isn't anythign else except True and False that could be translated automatically.

Karsten 7.

@Kuba You could also use ConversionRules or ConversionFunction

ExportString[<|"a" -> Identity, "b" -> True|>, "RawJSON",
ConversionRules -> {Identity -> "Identity"}]

Bases on the documentation only strings, numbers, True, False and Null have special translations.

Q: Logarithmic scale in a DensityPlot and its legend

I was recently faced with the task of creating a DensityPlot with a logarithmic colour scale, and with providing it with an appropriate legend. Since I could not find any resources to this effect on this site, I'd like to document my solution here. For definiteness, suppose that I want a plot of...

plotting color legending logarithmic-scale

Kuba

@Karsten7. interesting, but it is not documented, is it? That's quite convenient syntax:

ExportString[<|"a" -> Identity, "b" -> True|>, "RawJSON",
 ConversionRules -> {
   p : Except[_List | _Association | True | False | Null] :>     ToString[p]}]

@Karsten7. Which part of the documentation are you referring to?

Karsten 7.

@Kuba reference.wolfram.com/language/ref/format/RawJSON.html#Options

Kuba

12:18 PM

@Karsten7. I suppose I should've checked that. Anyway, it still fails if the key is a symbol. It cares only about values:

ExportString[<|"a" -> False, b -> True|>, "RawJSON",
ConversionRules -> {s_Symbol :> SymbolName[s]}]

Karsten 7.

@Kuba cf[s_Symbol] := SymbolName[s]

ExportString[<|"a" -> False, b -> True|>, "RawJSON",  "ConversionFunction" :> cf]

Kuba

@Karsten7. so officialy I can't read. Thanks ;)

Karsten 7.

Q: How does one set a logarithmic scale in a ContourPlot?

How does one set a logarithmic scale for both x and y axes in ContourPlot in Mathematica?

plotting logarithmic-scale

7 hours later…

YungHummmma

7:25 PM

Hey guys, does anyone know why Volume@RegionDifference[Sphere[{2.5, 2.5, 2.5}, 1],
Sphere[{2.5, 2.5, 2.5}, .5]] might not be working?

(returning 0)

Searke

8:16 PM

@YungHummmma break it down

Look at what RegionDifference returns

Once you see that RegionDifference isn't working as you expect

look at the documentation for it and look at the examples

you'll see you want to be using Ball instead of Sphere

YungHummmma

@Searke, why? I did look at the documentation, and it said "Sphere can be used as a geometric region"

ah, it's the shell...

It seems like it should say that in the main description and not the details...

Searke

Yeah. I almost feel like in an ideal world Volume would delay the evaluation and see that you're trying to find the volume of the difference of two sets with 0 volume and emit a warning.

@YungHummmma you looked at the documentation too closely. :)

YungHummmma

haha

yeah

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