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00:03
@J.M. I don't know why, but reading it I reminded me of an old anecdote. An old physics prof was asked why Latin was prevalent in science books when it has been already a "dead" language for many years. And he answered "They wanted knowledge in the hands of those able to read, for example, history".
@belisariusisforth That's a cool answer. :)
@J.M. He was old, but witty
 
8 hours later…
08:02
@Silvia @MichaelHale see the following graph
08:46
@ShutaoTANG Looks like you did it. Congratulations :)
@Silvia Thanks for your hint and suggestion. Maybe I have discovered a solution that deal with closed curve interpolation
09:04
The wolfram community page surely holds some world record for the webpage that needs ages to load..
Time to take that picture out again:
Mac users, if you find you cannot use CompilationTarget -> "C" anymore, this is probably because you downloaded new Xcode command line tools and you have yet to agree with the license. In order to agree, simply start Xcode and agree. Clang also suggested I run it under sudo to accept the license (in case you don't have Xcode, but somehow do have the tools).
@J.M. We need to make a new, more intriguing meme. Something mathematical. Something really slow..
@ShutaoTANG Glad I can help :)
@halirutan I thought it's only me and it's because of the "firewall".
@halirutan Well, there's large integer factorization. Still slow, or else crypto is in terrible danger.
09:19
@Silvia I can tell you here it feels like I'm directed behind your firewall..
@halirutan Welcome to China :D
@halirutan Like this?
@Silva You can use the VPN
@Silvia It's slow, but not too slow. Still faster than loading Community tho. :)
@ShutaoTANG VPN won't help here only if it's direct into WRI :D
In addation, the user could use this VPN for a hour for free everyday.
09:24
@Silvia Yeah, something like that. Probably more directly recognizable..
Still faster than Community.
@J.M. Thans your solution, maybe I have understood your idea
@ShutaoTANG When solving linear systems with periodic boundary conditions, you run into structures like that. So you fold it over.
@J.M. I would like to know what does periodic boundary conditions means.
@ShutaoTANG Like this.
09:41
@J.M. Unfortunately, our university library doesn't buy that paper:(
Alright, here goes: you have some familiarity with PDEs?
I had some classes about the numerical solution of partial differential equation last semester.
@ShutaoTANG One way of solving them is through discretization on a grid. That leads to the problem of solving large, banded linear systems.
Sometimes, one enforces periodicity in the solution, like in wave-related equations. That leads to the problem you presented.
After folding over, you might end up with entries in the lower left corner, upper right corner, or both (depending on the details). That's how you enforce the periodicity.
@J.M. I just known a little theory of PDE. like (1)discretization on a grid, (2)banded linear systems
@ShutaoTANG ...and you've now realized that B-splines also generate banded systems, yes?
Since they're zero outside a certain support interval, the coefficient matrix ends up being banded.
(Not so coincidentally, sometimes B-splines are used to approximate PDE solutions.)
09:50
Yes, the global B-spline curve interpolation generate a banded matrix
this is written in the chapter 9 of The NURBS Book
@J.M. However, I cannot find the paper that deal with closed B-spline.
Only a personal sites that described the construction of closed B-spline
@ShutaoTANG Isn't there any documentation included in the program you're using for closed interpolating splines?
In the Numerical analysis course, the teacher introduced the cubic spline interpolation
I have no doucumentation about closed interpolating splines, just trying do experiment
By the 3D- modelling software like CATIA, autodesk inventor to do experiemrnt
@ShutaoTANG Yes, and those lead to tridiagonal systems. It's all connected.
In fact, i just have interest on NURBS modelling. My majo is mechnical manufactuing
@ShutaoTANG I hope you now appreciate the effort that goes into writing mathematical programs; you really can't avoid experimenting and making mistakes.
10:01
@J.M. very happy to discuss problem with you. Also sorry for my poor english:)
@ShutaoTANG That's okay, I understood you just fine.
Mathematica is really a huge huge system. It's just impossible to know each function. I still keep finding very basic functions that I didn't know of. If people asked about those, they would get reprimanded and their question would immediately get closed as "easily found in the documentation". But it's not really that easy!
We should be more tolerant with these question.
So now here's my naive question that I'm embarrassed to post on the main site.
Histogram is bloody slow so I'm forced to use alternatives such as BinCounts or LibraryLink functions. My end goal is a visualization like that output by Histogram. Is there a simple way to get from something like the output of HistogramList to the graphics Histogram would produce?
Requirement: 1. Bin boundaries must have correct plot coordinates 2. I need both linear and logarithmic vertical scales.
Building from Rectangles and handling the log case, plus figuring out the best lower boundary for the bars in the logarithmic case is a lot of work and it's painful. I don't see how this can be done in 2 minutes. But I really hope I just missed some simple builtins (like when I missed the ScalingFunctions option of BarCharts).
@Szabolcs Some fiddling around with ChartElementFunction seems to be the only way to position bars. But, you've seen that HistogramList[] can do logarithmic binning?
10:38
@J.M. The binning I use is uniform. It is the vertical scale that needs to be logarithmic. For good visualization, this mean having to use log-ticks and having to automaticlly select a reasonable bar-origin (which is flexible for log-plots). It's just the visualization part that right now seems like a lot of work.
@Szabolcs In that case, nothing looks obvious to me, even after combing through the docs of BarChart[] and HistogramList[]. :( Maybe risk some embarrassment and ask it on main?
11:04
13
Q: Make a density list plot/histogram from large, pre-binned data set?

cosmoguyI have a large data set consisting of $\mathcal{O}(10^9)$ two-dimensional points. In order to save memory and time I have pre-binned these into a uniform grid of $500 \times 500$ bins using Fortran. When imported into Mathematica 8.0 as a table the resulting data look like: data = {{0.3883...

 
1 hour later…
12:12
I would love it if it said in the docs whether any given syntactic-sugar function was optimised in any way. SubstitutionSystem, for example, is just a wrapper to a NestList, according to PrintDefinitions.
4
@PatrickStevens Heh, and something somebody familiar with both L-systems and NestList[] would have written in one sitting. ;)
 
2 hours later…
14:25
Once in a while, you'll just see something with a very compelling title:
16
Q: Can a laptop battery explode while using Linux?

GortI have a 2013 Retina MacBook Pro, and I really want to install Debian on it. I have the know-how and have had at least three Debian systems before this. I am very knowledgable with the command-line and Linux's inner workings, and partitioning isn't an issue for me. So, I just have one question be...

 
1 hour later…
@belisariusisforth You could golf it further with AnglePath[] in 10.2 and later. I know you're on 9, but I did write an equivalent for older versions. :)
@J.M. Nah, I already spent way too much time on that silly thing :)
@J.M. And I don't visit the CG site anymore. They are too golfing-languages-oriented there
16:06
I don't know what to do with posts like this one:
0
Q: Report a bug for Image-Tool

yodeMy version is In[2]:= $Version Out[2]= "10.3.0 for Microsoft Windows (64-bit) (October 9, 2015)" A fun thing that I think it is.The bug is introduced in 10.0.0,but it's still now.You can reproduce it via use any button in Image-Tool like this: The Mathematica will pop up a error message win...

Of course this is not the place to report bugs. We're not Wolfram.
But then I don't want a clearly spelt out policy about disallowing this either, for many reasons ... it's very easy to get into a blurry territory between a bug report, a question about whether it is a bug and asking for workarounds. Just knowing about some bugs can be useful too sometimes. Still, this is not even a question, and when posted like this I see no other choice than to close it.
@Szabolcs If it's not officially a question, it's game for closure. Of course, "is this a bug?" circumvents that.
Then there's another thing: I'm sure many people use a pirated version (especially students in developing countries like China where piracy is rampant and universities won't or can't purchase a license ...) They can't contact support. But it's still best if WRI learns about all bugs. I'm hoping people wanting to do this will go to W Community instead of SE though.
17:10
Hello guys. I have a quick question: if I have a list like {a1,{b1,b2,{c1,c2,c3}}}, how do I convert it to a1[b1,b2[c1,c2,c3]]]?
acl
acl
@halirutan how about this?
the (ahem) joke is that it's a log, which is slower than any polynomial. ha-ha.
@J.M. When I read things like
> Some Apple hardware has been known to have issues under ALL other operating systems (not just Linux Kernel based ones) - due to Apple's proprietary hardware and more specifically their proprietary fan controllers
I just want to pick my monitor up and start banging it against the wall in a rage until it breaks up into small pieces, then burn them.
@Pragabhava How about
 {a1, {b1, b2, {c1, c2, c3}}} //. h_[a___, x_, {s___}] :> h[a, x[s]]
17:25
@JacobAkkerboom Thank you!
@Pragabhava You are welcome! Just note that it is not a very common thing to do I suppose :).
@JacobAkkerboom I know. I guess is the classic XY problem. I have the list {a1,{b1,b2,{c1,c2,c3}}} and I'd like to view it as a tree. I've tried TreeForm but it displays all the headers.
@Pragabhava Ah, I didn't know about the XY problem. Nice know about it :).
17:41
@JacobAkkerboom Trough out the years, I've become a master in providing examples :P
 
1 hour later…
18:44
Sorry to bother you again guys. Is there a way to prevent TreeForm from displaying the last element of every branch?
19:28
@Szabolcs There is nothing preventing anyone from contacting support. You can file a bug report without giving a license number or activation key
4
Very often, people will send an email that's somewhere inbetween asking for help and reporting an issue. That you can't do without an actual activation key. But if you want to report a bug, you just have to send an email to [email protected] and say "hey I think this is a bug"
 
2 hours later…
21:14
Response time could be better. I sent a v10.3 bug report four days ago and I'm still waiting for a confirmation... other than that automatic one.
22:00
is it possible to download the trial version of Mathematica v10.3 ? could you please post the link?
22:18
@Pragabhava That one sounds kind of tricky. If you have held expressions, the following does not work, but otherwise, you can use TreeForm on this:
MapAll[Function[Null,
  If[! AtomQ@Unevaluated@#, Unevaluated[#][[;; -2]], #],
  HoldAll], expr]
 
1 hour later…
23:35
@Searke That's a very good policy, methinks.

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