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6:02 PM
Hi all
@belisarius hi
Can somebody test if the results in my Q are reproducible in other machine?
In[8]:= k = RandomInteger[4, 6]

{2, 2, 0, 3, 3, 0}

woops, gimme one sec.
6:10 PM
@belisarius I got the same result in both cases.
damn, so it is my machine
Sorry. There.
Heike : Pls check with a list adding up more than 7
@belisarius What do you mean?
Do you mean replacing the 7 in lw with something larger?
@Heike Be sure that the result from RandomInteger[4, 6] is a list adding up more than 7
6:15 PM
Sorry, lets try that again
@belisarius I also get the same result both times. Possibly you have a stray definition for lw hanging around?
@OleksandrR Nope. I restarted Mma several times ...
@belisarius What version are you using? ...
6:20 PM
I'm on 8.0.4. Maybe it's something that got fixed in the last update.
I'm on 8.0.4 too.
Ok. deleting the Q. Sorry for the annoyance.
You better be.
hi all
6:24 PM
@CHM Says he who keeps complaining to us about biology.SE ;-)
The nagging was obvious.
@Heike you should check it out, btw. Just take a look at some of the questions/answers.
There's not a single 10+ upvoted "active" question...
@CHM indeed:
Q: Effects of beer on muscle recovery after exercise

zellerI noticed it several times that when I drink beer (even one bottle) after some heavy workout, the next day my muscles are more stiff than other times, and not the same way... Is it because that lactate and NADH levels are raised both due to the anaerobic training and alcohol metabolism?

BTW, I've updated the stats of the beta proposals.
sounds a lot like Skeptics :)
@Fx I was about to comment on that question as well.
6:30 PM
@Fx that's not the worst :P
@CHM The first picture is broken
@Heike for some reason, they're all going down.
Everytime I reload, one goes out.
Q: Does GFAJ-1 use Adenosine triarsenate as its energy currency?

PeteRegarding the bacteria found in Mono Lake, CA that scientists believe uses or can use arsenic in its DNA backbone where life as we know it uses phosphorus (according to their experiments depriving the microbes of phosphorus and providing much arsenic), have researchers conjectured and tested whet...

@Heike weird behaviour.
They came back, but now some are gone forever, apparently.
Q: Why is the Vagus Nerve (CN X) the principal nerve of the parasympathetic nervous system?

MasiMy professor says The principal nerve of the P.S. is n. vagus X, descends together with the large cervical vessels into the thorax and abdomen where it gives off visceromotor fibres to all visceral organs, forming visceral network - plexus (down to flexura coli sinistra). Nervus Vagus...

I'd be tempted to answer with "because God wanted it that way", just for the fun of it :)
6:32 PM
@CHM Maybe with all the pictures the loading time is too long.
@Heike I uploaded them to imgur the first time. Now uploading directly to stack.imgur
@Fx That dude, masi... is an annoyance.
@CHM probably why they were dropping out. imgur doesn't store them forever.
@Fx :)
@rcollyer I thought they stored them for 6 months at least?
@rcollyer I've uploaded them about an hour ago.
@Heike I don't know their time frame. maybe a caching issue?
@CHM I saw.
6:38 PM
@Fx you need to look at the users' profiles, too. This guy Masi, spamming the hell out of the board with his wikipedia copy-pasting and self-answering, is med student.
The images should be fixed now.
@CHM Did you see his SO profile? 709 questions! Some quite good. But, a lot of questions ...
@rcollyer don't worry, I've got him under surveillance.
I might be a bit too harsh in some comments, but I feel offensed.
I feel offenawk
@rcollyer I feel obligated to share this every time someone mentions too many SO questions and it's not this guy that they're talking about :)
6:47 PM
s/awk/sed/ :)
offensed -> offenawk
sorry :)
@Fx he's an offended hawk
Might should have used offen ded
@belisarius no apologies. it made me laugh.
@CHM often dead?
6:49 PM
a dead hawk
@yoda Stunning. Just stunning.
hi yoda!
@Fx often. Always would be an annoyance.
@yoda His highest rated question:
Q: XKCD SQL injection - please explain

BlankmanJust looking at: (Source: http://xkcd.com/327/) What does this SQL do: Robert'); DROP TABLE STUDENTS; -- I know both ' and -- are for comments, but doesn't the word DROP get commented as well since it is part of the same line?

@yoda good grief. It's like every time a question pops into this guy's mind, his first thought isn't to have a bit of a think about it, but rather to post on SO.
6:51 PM
little bobby tables?
yep, little bobby tables strikes again.
@rcollyer Even I got that joke, and I don't know anything about SQL.
Wow. I wondered what smelled like dead meat... I felt bad for an instant: did I throw some minced beef in the bin? No... the dog farted.
@OleksandrR That list doesn't even show all the deleted questions. I'm sure the count is 1.5x that from a mod's view
@CHM Not the hawk?
6:52 PM
@yoda minimum.
@Heike dead hawks don't fart
But they smell after a while
@Heike no wordplays this time. Not even my nose playing games with me - only real, invigorating dog fart.
live rottweilers do, I assure you
@rcollyer okay, I just have to ask: why is your chat username italicised?
6:53 PM
@Fx room owner
@yoda this is an ex-hawk
It's pushing up the daisies
@Fx never noticed that. But, me and Szabolcs have that job.
a python fan!
Of course
6:54 PM
@yoda Not really. It is an okay language.
@yoda oh, I see
@rcollyer that XKCD is funny.
@rcollyer innkeeper, a pint of your best cider!
@CHM True, but I like this variant:
6:55 PM
@CHM if that seems funny, take a look debuencomer.com/argentina/inserts/jofre/calidad.php
@belisarius what am I looking for there?
Will do in a sec.
@Fx I miss cider in London.
Hmm. Personally never really found XKCD that amusing. I much prefer SMBC (darker humour and broader range of topics).
@rcollyer so do I! and it's not easy to find in Paris :(
6:57 PM
Warning: mysql_connect() [function.mysql-connect]: Access denied for user 'nx000043'@'localhost' (using password: YES) in /home/nx000043/public_html/argentina/inserts/jofre/conexion.php on line 11
Error conectando al servidor
@Fx I'm much farther away from London than Paris. At least in Paris, you could, in principle, hop on a train ...
@rcollyer The page was hacked with an injection
@rcollyer I had this one hanging on my wall for a while:
user image
@belisarius ah.
@Heike I stopped myself before trying to solve it!
@Heike Too true!
6:59 PM
@rcollyer haha.
I've hesitated between learning python and MMA, actually.
@CHM the problem is not learning, it's using regularly
if you don't use it regularly or enough, you'll just forget it
for python, I don't use it enough, and everytime I do write some it takes me ages to find again how to do the basics
@CHM as I've said before, when you know Mathematica, Python's trivial. I picked it up in a few hours after a friend suggested to write something in it that I'd prototyped in Mathematica.
@CHM I had a job opportunity that would have required me to learn python. It's not a bad language, and easily learnable.
@Heike So with your number obsession, how difficult was it to train yourself not to try to solve this?
7:02 PM
@OleksandrR I should give it a go then.
@rcollyer I must admit I've spent some time on that thing.
@Heike :)
@belisarius I'll save that one for later.
@Fx Agreed. As with everything else, I guess.
@OleksandrR @rcollyer But even if it's easily learnable, is it really worth it, for the intents and purposes of a scientist?
@OleksandrR This one hit home. A friend of mine is suffering from a severe case of something like Crohn's, and can chug the barium shakes. It makes the radiologists want to vomit. :)
@CHM A friend of mine in astronomy uses it almost exclusively.
7:10 PM
@CHM many will agree that it's definitely worth it to learn. It's also a general purpose language, unlike mma et al., so you have a lot more flexibility in what you can do
@belisarius LOL
@yoda The only thing that put me off Python was that I had to choose between too many versions, unlike with MMA, where I just get the most recent.
gotta run.
I wasn't quite sure if I'd have to go with 2.x or 3.x
@CHM uhh... then why not do the same for python?
And as MMA was available at uni, I got it.
7:12 PM
It's only between p2.7 and p3 that there's a major change. Stick with p2.7 if you only need p2.x and p3 if you want to develop for 3+
@CHM That's why I have a Mac :-)
But I have to go as well.
@Heike I have a mac too. But it comes with 2.6.x, which is apparently not advised
But still, I don't know much about it.
@yoda nice.
All you'll ever need to do with installing python. No more worrying about glibc and crap errors and make files and breaking your ass over installing matplotlib (especially on a mac)
Free for academic use, so you just need to enter your univ id and they'll send you a link
7:15 PM
Oh, but that's commercial...
Oh, ok.
@CHM my motivation was that nobody else in my university seems to use Mathematica, so it's not installed on our supercomputer, whereas Python's available everywhere. That said, I do very much like NumPy's advanced indexing. It's absolutely mind-bending at times, but highly flexible. Since questions came up here on the subject, I've been toying with implementing it properly in Mathematica if I get the time.
My bad.
No, it's ok. Chat is behaving weirdly for me... messages keep coming in dumps and I can't tell if someone's seen something or not
@yoda @Oleksandr thanks. Be back in ten minutes.
@OleksandrR while you're at it, could you also throw in a logical indexing? ;)
7:20 PM
@yoda also, for Windows, there's lfd.uci.edu/~gohlke/pythonlibs
@yoda logical indexing isn't much different than Pick, IMO. Problem is, logical indexing returns a masked view onto the original array, not a copy like is usual in Mathematica. Not quite sure how to deal with that kind of issue in general.
@OleksandrR Sure, I know how to do an equivalent in mma, but there is something neat about being able to do a={1,2,3};a[[{0,1,1}]] and getting back {2,3}. Of course, this is just an old habit and I try my hardest to not transfer habits between languages. It's more of an will-this-be-possible-in-mma kind of thought
@yoda I had in more in mind to enable things that are tricky to do in Mathematica usually, like e.g. applying a set of Spans along an axis of an array. Main problem is, I find these even less intuitive than the (infamous?) second argument of Flatten...
@yoda for instance instead of Transpose@Apply[{Part[#1, ;; 200], Part[#2, ;; 190], Part[#3, ;; 175], Part[#4, ;; 155]} &, Transpose[array], {1}]; (which I need to use regularly), one might write array[[{1, 2, 3, 4}, {{;; 200}, {;; 190}, {;; 175}, {;; 155}}]] with advanced indexing as in NumPy.
7:42 PM
@OleksandrR ah, yes. That would be immensely helpful
@yoda currently downloading enthought.
at a steady 35 kB/s.
Are you from 1995 o_O
@yoda Pick[{1,2,3},{0,1,1},1] ?
I was going to write "that's so 1998" but, I didn't.
I'm now at 9,2 kB/s
It's their server.
@OleksandrR There have been moments where I almost understood the second argument of Flatten.
7:48 PM
@Heike I know, the point wasn't that it wasn't possible, but I see writing it that way as writing Plus[a, b]
@Heike yes, I use it quite regularly myself. But I usually find my initial idea of what it's going to do, is not what it really does. Thus an experimental approach to coding is sometimes called for.
Then again, perhaps I don't help myself by always choosing to work with data in the form of 5- or 6-dimensional arrays.
Are you dealing with "heterogeneous" lists? Something like {{a,b},{c,{d,e,f},g}}?
Because I've never had problems with Flatten[], but my lists are mostly homogenous in size, e.g. {{a,b,c},{d,e,f}}
@OleksandrR My brain breaks when I go deeper than level 4.
@CHM if that was meant for me, no; my arrays are full-rank. I just find it gets a bit non-intuitive to imagine what an argument of {{4}, {1,3}, {2}} will do.
Perhaps my array-visualisation is not as good as yours, however.
OK, time to go home. TTYL, everyone.
8:21 PM
Back again... just a short walk home for me!
This is annoying me to the point of wanting to break my computer
Q: Are cells really the basic unit of all life?

LanceLafontainecommented: @CHM, just because a question does not have a clear-cut answer, it doesn't mean it isn't a valid question. Exploring such questions and explaining why or how is what scientific thinking is about.

Yes, biology...
"Break wind, not computers"
HAL had no cells ...
or something
I have to say the guy's bio and picture make me treat him more harshly than I'd normally do.
He seems not to think before asking the question.
Anyway, flagged it off-topic per the FAQ. We'll see what happens lol.
8:33 PM
Maybe you should become a mod on biology.se
"I am interested in all things related to biology and chemistry"
That is a lot
@Heike I'm actually thinking about joining their community.
@belisarius vain.
@belisarius I mean, sure, we're all interested in many different topics.
But... from his questions, he's more interested in being nurtured than anything else.
@Heike and then I'd stop annoying MMA.SE with other people's troubles :P
@CHM Well, you know. The answer is 42
@belisarius Haha.
Maybe we should have a stylised "42" as our logo.
Or incorporate it somehow.
@CHM Clap!
8:49 PM
@CHM "I voted to close this question as I don't like your face." ?
@CHM you should probably take a break from biology.se... have you tried not visiting? ;)
@yoda Maybe he could get himself voluntarily suspended for a week
probably a lot longer...
I'll post the full suite of pics on the weekend, but thought this was worth noting.
Questions/day has come down a bit lately and we are about to get the Easter holiday, which might reduce traffic.
But all in all, this is good progress over the last fortnight.
9:06 PM
@Verbeia good progress indeed. Thanks for posting. I must admit I'm a little surprised at the strong upward trend, but I suppose it shows that we're probably not too near to saturation point, which is good. Should get to 1500/day easily if this carries on.
9:17 PM
@OleksandrR "Hot" questions seem to be quite important in attracting new users/views.
Anyway, off to work. See you later.
Speaking of hot questions, there always seem to be a lot of scifi questions in the hot questions list.
@Verbeia that sounds reasonable, though TBH I'm not so sure if the "hot questions" we've had so far really represent the best that our community has to offer. It seems to be quite arbitrary which questions turn out "hot".
@Heike I think because most of the scifi/fantasy questions are totally subjective, so it's easy for five or six people to give their opinions without duplicating one another. Problem-solving questions of the kind we have here are obviously much more objective, so I suppose it's just the fact that things can be done in so many different ways in Mathematica that makes "hot" questions relatively common for our site.
@Heike for example this question seems to me quite ridiculous: the obvious answer is "because it's a fictional scenario" but the actual answers are various different quasi-plausible rationalizations of the obvious contradiction.
1 hour later…
10:55 PM
all, I have a problem and have a feeling it is silly. in its most simplified form, consider
t = {1, 2};
SparseArray[{{p_, p_} \[Rule]
t\[LeftDoubleBracket]p\[RightDoubleBracket]}, {2, 2}]
which evaluates to the right answer but tells me that Part::pspec: Part specification p is neither an integer nor a list of integers.
how do I avoid this?
what am I missing?
Oh yeah, there was a question on that... hold on
Is needed?
The tag-wiki for says both 2D and 3D.
@acl bah. Can't find it.
But to answer your question, use :>
@yoda damn, I knew I was being stupid
Part doesn't like getting symbols that evaluate right away, but don't mean anything to it — i.e. not an integer or a span (list)
11:09 PM
no problem :)
@rcollyer I don't see a harm with having it... some issues/options are kind of specific to graphics3d, so I wouldn't remove it
what was the MATLAB question you had @acl?
@yoda are you going to be here in 5 min? I need to fix something first
yeah, i'll be here.
@yoda so basically it was not really a concrete question.
the situation is, I have a program which may be formulated in matrix form (construct large sparse matrix, find eingenvectors, construct other matrices from them etc)
and right now I have it in mma and scipy. they're roughly equally fast
I am really limited by the speed of this thing, so have to get it faster. I can't think of doing anything other than rewriting it in matlab, but that'll take me a few days as I am not used to writing nontrivial programs in it
so I am trying to decide if it's worth the effort
now, I remember you and JB saying that you find matlab faster or more convenient (I don't remember) for some things. could you indicate what kind of thing you find easier there? what faster? or do have you not used both for similar problems?
I just don't know how to find out short of writing the program twice, and I don't know anybody (in person) who can write decent mma code (in terms of speed for numerics), so I remembered that discussion and decided to ask
11:25 PM
I have not used both for problems on the scale you're talking of, but I generally find matrix operations — constructing, indexing, slicing, reshaping, flattening etc., simpler in matlab.
If you can describe your problem or piece together an example that shows the core of what you're trying to do, I can try and port it to MATLAB and see if it makes a difference
That is, assuming it's not a huge project with many loc
@yoda thanks, I doubt the translation can be done much faster by anybody else. it's just that there's lots of moving parts
so I can't give a simplified version
But from what I've heard, well coded MATLAB will only be slightly faster than well coded numpy
If you really want to speed it up further, you'll need to interface with C/Fortran
so you have not noticed significant performance differences? (don't worry, I'll use your answer to decide, then forget you ever said anything about speed :) )
I don't use python — I've only heard about this. I've noticed differences between mma and matlab for sure, with matlab being faster.
How big are your matrices?
@yoda but from experience, if I do it in C it's marginally faster than mma (if matrices are the bulk of the work) and takes me much, much longer to write and debug
@yoda the size isn't a huge problem. they're up to 50000 by 50000 in extreme cases but sparse; but that is the same for both mma and matlab
and scipy is all good, but when I am forced to write actual code it slows right down. julia is nice but not available on our large machines
("actual code" meant "actual python code")
11:43 PM
hmm... my gut tells me that it might be faster with MATLAB going by what I've noticed. However, I can't say for sure, without knowing the problem... since you say that there are other moving stuff and operations, it could be an area where matlab doesn't shine or needs excessively long code to do...
but remember we're comparing to mma...
well, I guess I will just do it and see what happens. how hard can it be? :)
it's not like I am committed to more projects than I can deal with already...
for example, say you have two vectors/matrices a and b and you wanted to do some f(a,b) and index the output (assume also a vector/matrix), you could do something like f[a,b][[index]] in mma, but with matlab, you can't do that. You'll have to do something like temp=f(a,b);temp(index)
well, thanks anyway
so that involves an additional copy of the output
yes I see
11:49 PM
If you vectorize your code, things are way faster in matlab than mma. Use linear indexing when you can. Sometimes flattening to a vector, doing all operations as a vector (where permissible) and then reshaping might be faster
well, if that is the case, I think I'll give it a shot
use bsxfun for element wise operations on matrices/vectors... might take a bit getting used to, but nothing like 2nd argument of flatten :)
that was the impression I got from playing with it some years ago, but I know more tricks in mma now. then again I notice that for large projects I tend not to use complicated speed-up tricks because I am already at my limit thinking about the physics and don't have the capacity to optimize much
Yeah, do give it a shot. Nothing to lose :) (well, except for your time, if it doesn't work out... )
@yoda that I got partially and briefly, and now it's gone again...
that's what I will probably do over the break (family? friends? relaxation? what?)
11:53 PM
ha, the sad life of a researcher ;)
really, conferences are the only saving grace.
@yoda thing is, I don't like conferences or travelling
I kind of do... attend 2 days, goof off 3 days. Can't argue with that. Add to that a week of post-conference laziness, and I've got a solid ~2week "holiday"
luckily, my institution is an extremely active conference centre; there's one every week or, at most, every two weeks. so I don't need to move much, people pass through at the rate of (I think) 1500 visitors a year... or so I read in some report, and I believe it. it's good for someone like me!
ah, yes. Yours must be a busy place — lots of free food :P
Oh wait. THat's a US only thing.
@yoda well food is free for the participants, and I can technically register for any conference here for free, so...
not that I do that of course :) but the tradition of bribing people with food to attend seminars etc is not restricted to the US
11:59 PM
@acl oh, that's not what I meant. Here, there's a conference going on every time and they order excess food (yeah, wasteful...) and they send out an email to the gradstudents list to come grab it all (not participants at the conference)
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