Reputation
66,449
Next tag badge:
116/100 score
18/20 answers
Badges
5 148 279
Newest
 Nice Answer
Impact
~701k people reached

Apr
12
comment Importing a large Excel file
@P.Fonseca JVMArguments works for me in 10.4 but it is not documented. This is a thing I truly consider a bug of the documentation. What I don't understand is that specifying the CommandLine didn't work at all under OSX.
Mar
20
comment Why one needs two Unevaluated to show 1+1 correctly in TreeForm?
It's not entirely clear. On the one hand, if you use a LinkSnooper to monitor the communication between FronEnd and Kernel, you clearly see that the kernel sends the wrong result back. On the other hand, if you use math in a terminal session, you can call TreeFrom[Unevaluated[1+1]] and it gives you back a tree-form where the 1+1 is not evaluated. But the Unevaluated isn't stripped either. Therefore, I think the issue is in the kernel, but the kernel behaves differently when it is attached to a graphical FrontEnd.
Mar
19
comment Why one needs two Unevaluated to show 1+1 correctly in TreeForm?
Exactly and why is that? Because #& is another function that is called and that leaks evaluation! Look here. In general, Leonid has a bunch of very advanced answers around the topic evaluation control, but they might be a bit too difficult for beginners. This is why I wrote up an answer to this question, because it gave me the opportunity to discuss a very small detail that might lead to people thinking about this topic.
Mar
4
comment Rendering a shape rather than a point in Graphics
It's a bit funny, because you are building the Graphics yourself and you're not using ListPlot. It is a very small step to use Rectangle instead of Point and I wonder why you haven't just tried that?
Feb
17
comment P-values differ in tests for normality between Mathematica and SAS
@Lucas Just post the question on Cross Validated and comment here giving me the link. I could look over it and improve it if it is really necessary. Another thing: Can you make a distribution test against a specific distribution in SAS as well or is this what SAS is already doing? Otherwise, you might want to see whether there are different p-values as well.
Feb
17
comment P-values differ in tests for normality between Mathematica and SAS
@Lucas Another, even better suggestion is to ask the question, why p-values might be different for tests against a specific distribution on Cross Validated. Refer in your question to this Q&A here and mention Mathematica, but don't make the question specific to Mathematica so that it isn't off topic there! The reason is, over there the user whuber is mod and very knowledgeable AND he is a high-rep user on this site as well. Therefore, he knows Mathematica very good and probably won't hesitate to answer.
Feb
17
comment P-values differ in tests for normality between Mathematica and SAS
I'm not a statistician, but purely from the standpoint of using the p-value as indicator whether your sample was drawn from a known distribution it makes a difference for me if I (a) KNOW that I test for normality or (b) I test against another distribution (which happens to be a normal distribution). In case (b), Mathematica obviously accounts for that by adjusting the p-value accordingly. If you want ta detailed answer, I would give support@wolfram.com a shot.
Feb
17
comment Expressing the n-th power of a matrix
Hehe.. I knew from the beginning that this answer would be too large and should not be given here :)
Feb
17
comment Expressing the n-th power of a matrix
Yes, I was very close to mention DiagonalizableMatrixQ, but I thought that might be to much information in this specific case. But I may be wrong and I should include this hint. I have added it now.
Feb
2
comment How to apply a user-defined function to a list
I have no idea what is possible in W|A Pro, but when it takes real Mathematica syntax, then you should try to define your function as f[n_]:=351n^(-7/10)
Jan
30
comment Parallel compiled functions running on parallel sub-kernels
I'm not sure I understand. Or maybe you misunderstand what I'm doing. In the first example, I run f[data] on the main kernel exactly one time. Takes 9.1 seconds on V10.3.1. Then, I'm calling it 8 times because I have 8 subkernel and it only needs 24 seconds which tells you that one single run indeed only needed 24/8=3 seconds. We are talking about two different parallelizations here. Parallel threads and parallel sub-kernels and I combine both to squeeze the last bit out of my CPU. Ping me in Mathematica Chat if you have further questions.
Jan
26
comment Convert (rescale) 16 Bit png image
Have you inspected your data carefully? It seems that image histogram leaves out values > 250, because the gap of 8 does not hold for all your data. Please look at DeleteDuplicates[imageData] // Sort and after that BitShiftRight[% + 1, 3]...
Jan
24
comment Fast loading of png files
The Import/Export framework is pretty large because it needs to check for all kinds of possibilities. You can distill it down to a call of the function Image`ImportExportDump`ImageReadPNG["tmp/test.png"], but even that does only speed it up a small amount. I'm not sure you can make it really fast without writing external code that calls a fast library. Can you provide your exact system and a sample "PNG"?
Jan
24
comment How can I create a random symmetric matrix in this way?
Sorry. Saw it and thought I need to clear this up as quick as possible so that no one believes it is a good way.
Jan
22
comment List of Mathematica related acronyms and their real meaning
@Mr.Wizard and all others: I made my answer community wiki. Please help to make this a useful post and clear up some of the vague Wolfram marketing speech.
Jan
22
comment List of Mathematica related acronyms and their real meaning
@Moo Let me work this in later.
Jan
22
comment List of Mathematica related acronyms and their real meaning
@MikeHoneychurch I have added the Bloomberg information.
Jan
22
comment List of Mathematica related acronyms and their real meaning
@Moo Ha, haven't seen this. Everything counts that the community is interested in. I wouldn't take SystemModeller because it is far off of Mathematica, but I believe it is a good thing to clear up related technologies.
Jan
22
comment List of Mathematica related acronyms and their real meaning
If you feel that I missed some important thing, then comment and I'll add it to the list. I have not included all link technologies but only the IMO most important ones that have many questions here on SE. Additionally, please help to clear up WPC, WPL, Mathematica Online, W Finance, W Discov P, W Data Framew. What exactly are they doing and how do they relate to Mathematica?
Jan
20
comment Is it possible for librarylink function to be Listable like that in Compile?
That is because their highlevel code (the part before the LibraryFunction that is used as fall-back) is the same as the compiled library code. I suspect that when the function is too easy (like returning only x), then Mathematica detects this an doesn't bother to call the library function.