Wolfram Mathematica

Sjoerd C. de Vries

02:02

Anyone in here?

Rojo

Hey

Sjoerd C. de Vries

Hi Rojo!

Rojo

Whats up @SjoerdC.deVries

Sjoerd C. de Vries

Just arrived on the final leg of my vacation. Finally wifi again.

Rojo

Nice... How long is the leg?

Sjoerd C. de Vries

02:04

6 days Anything of interest happening the last couple of days?

I lost my contiguous presence streak somehow

belisarius

@SjoerdC.deVries Hi!

Sjoerd C. de Vries

Hey @belisarius

belisarius

Did you got to the center of the earth?

or came short?

Rojo

@SjoerdC.deVries Well, I haven't been very active this week up to last night

I even asked Mr.Wizard the same yesterday

Sjoerd C. de Vries

No, I missed the entrance, but I was close: 13 km of the Hekla vulcano

Rojo

02:07

Hey @neighbour

belisarius

@Rojo hi!

Sjoerd C. de Vries

How is it in the third world nowadays?

Rojo

Great

belisarius

@SjoerdC.deVries I was re/rereading the book with my son a few months ago. The descriptions of Iceland are very impressive

Rojo

Bus prices just went up 100%

Common stuff

Sjoerd C. de Vries

02:09

Just use cars. No problemo

Rojo

You park it for me? :)

belisarius

@SjoerdC.deVries USD 5 per gallon :D

Sjoerd C. de Vries

That's what drivers are for, aren't they?

In the Netherlands its €1.7 / liter

belisarius

@SjoerdC.deVries Do you need a maid? I can find one here that can program Mma almost for free

Sjoerd C. de Vries

:)

Family of yours?

belisarius

02:13

@SjoerdC.deVries Well, I cook pretty well

I am nice with kids

responsible

Sjoerd C. de Vries

I saw your BBQ picture on seasoned advice

belisarius

Oh no! that was an Internet photograph ... my bbqs are much better

Sjoerd C. de Vries

Well, I'm working to lose weight so BBQs on your scale is something to avoid.

In that context, vacationing in the US is dangerous

belisarius

@SjoerdC.deVries Losing weight. Learning Wavelets. Exercising. They are all in my schedule

Rojo

@belisarius Where are you learning wavelets from?

I'm interested

Sjoerd C. de Vries

02:18

I'm almost at my set goal, I'm now at 83 kg with my 6 ft 4 frame

belisarius

@Rojo Not yet, but I have a list. I will look for it tomorrow

@SjoerdC.deVries You were on diet on vacations? That is sinful!

@Rojo Did you try my exclusions question?

Sjoerd C. de Vries

Well, I started before that. Just tried to not gain to much. Pretty difficult here, given the uhuge portions you get in the restaurants here.

belisarius

@SjoerdC.deVries What is the typical food there?

I am always interested in learning about the important things in life: food, food, and something else I never remember

Sjoerd C. de Vries

Breaded and deep fried stuff. Lots of cheese and fat.

belisarius

@SjoerdC.deVries Fishy or meaty stuff?

Sjoerd C. de Vries

02:26

Everything. I've head tuna, haddock, shrimp, but also chicken and steak.

belisarius

sounds interesting!

Sjoerd C. de Vries

I usually pick just an appetizer and steal a few gfrench fries from my kids

belisarius

hi rc!

rcollyer

hola! Just checking in.

@SjoerdC.deVries how's the trip going?

Sjoerd C. de Vries

Hi rcollyer

Im now very nearby I suppose

Arrived in cape cod this afternoon

rcollyer

02:29

Ah, Massachusetts. Nice.

Sjoerd C. de Vries

Got ripped off in NY

rcollyer

Well that sucks.

Sjoerd C. de Vries

Remember my $13/night wifi?

rcollyer

Yeah.

Sjoerd C. de Vries

It happened to be per device...

We have 4 iPhones and 2 iPads

rcollyer

02:31

Seriously?

Ick.

belisarius

@SjoerdC.deVries You can ^&^&$## here all night for $13

Ask Rojo

Sjoerd C. de Vries

Talked it down to 3, but it sucks anyway

rcollyer

How do they justify that? Idiots.

Sjoerd C. de Vries

Policy, hohum

You can buy a whole access point for that amount

rcollyer

I was thinking something along those lines ... buy an access point (no more than $20-30 required), and set up your devices to use that, while the point is the only thing that accesses their network.

belisarius

02:34

@SjoerdC.deVries How did they knew all those devices were yours? did you use the same access key for all?

rcollyer

They may get a little pissy with that, but who cares.

Sjoerd C. de Vries

You had to go through an access page and press lots of accept buttons. I guess they check MAC addresses

Charged to the room

rcollyer

sounds to me like you'll be using their hotel again.

Sjoerd C. de Vries

Not bloody likely

Well, perhaps, but I won't use their wifi

belisarius

I remember with nostalgia those days when I didn't care about the connectivity at the hotel

rcollyer

02:37

the sarcasm tags seemed to have been stripped, again.

Rojo

@belisarius Sorry, I'm not getting pinged properly and my firefox is about ot die

I don't blame it with the number of tabs I have

Sjoerd C. de Vries

@belisarius I wonder about that ^$^$## thing?

Rojo

@belisarius Could you link me to the exclusions question?

rcollyer

@Rojo weird. I'm running about 30 right now between 3 or 4 windows. You?

belisarius

@SjoerdC.deVries Ask Rojo. He is younger

Rojo

02:39

@rcollyer Only 78

I've been at 250

belisarius

4

Q: Managing Exclusions in Plot[]

When I do: l = {5, 6, 6, 5, 6, 6, 5}; f = Interpolation@l; g[t_] = D[f[t], t]; p1 = Plot[{f@x, g@x + 4}, {x, 1, Length@l}, Evaluated -> True, Exclusions -> True] I expect: However, since Plot[] doesn't detect the discontinuities, I get: I have two ways to overcome this, ...

plotting

rcollyer

@Rojo and I thought I had a lot open. :)

Sjoerd C. de Vries

@belisarius I'm a gentleman, we don't discuss things like that.

Rojo

@rcollyer I don't like boomarks :P

rcollyer

@Rojo apparently not. Oh well. Firefox can handle it, maybe.

belisarius

02:41

@SjoerdC.deVries I thought int'l goods prices were of your interest.

Sjoerd C. de Vries

@belisarius how old are you actually, if I may be so rude to ask?

belisarius

@SjoerdC.deVries I am 13, since my last divorce

Sjoerd C. de Vries

;)

belisarius

brb

need something to eat

Sjoerd C. de Vries

20 sausages?

belisarius

02:46

@SjoerdC.deVries perhaps a hamburger. Alone tonight

Sjoerd C. de Vries

How about a salade nicoise

rcollyer

@belisarius so only 10 then. :)

belisarius

@SjoerdC.deVries remember YOU are the one on diet!

rcollyer

Hi, @Verbeia!

Sjoerd C. de Vries

I'm fascinated by food all the time, just because of my diet

belisarius

02:47

@rcollyer sounds nice. yesterday I had lamb. superb!

rcollyer

@belisarius yum.

Sjoerd C. de Vries

I don't like lamb that much

belisarius

I am starving. See you l8r!

Verbeia

Hi all, I'm back. I thought this was interesting. I wonder if there is a community with the momentum we had for Maple

1

Maplesoft

Proposed Q&A site for users of all experience ranges with Maplesoft's numerical analysis software.

Currently in definition.

Sjoerd C. de Vries

@belisarius bye

Hi @Verbeia

rcollyer

02:49

@Verbeia could be interesting. They need 40, 10+ questions, though.

In the interests of not having proposals languish, of course.

Verbeia

In three days we had that already.

Sjoerd C. de Vries

I just received the Founder badge

rcollyer

We only had 21 questions, total

And, 11 at 10+.

belisarius

How could I automatically translate all my Maple stuff into Mma and be happy?

3

@Verbeia Hi and bye!

rcollyer

@belisarius go get food, already!

Verbeia

02:53

@rcollyer the rules were different then. I have no doubt we would have worked out the extra questionsin another day or so.

rcollyer

@Verbeia No doubt. Just I think the increase in questions will do more harm than good.

Rojo

@belisarius You used Maple?

On your question, how about deleting the vertical or "almost vertical" lines in the plot?

Verbeia

Anyway just dashing in and out. Back later, see you.

rcollyer

bye.

belisarius

@Rojo Just enough to be sure that there are better things under the skies

Oleksandr R.

02:54

@Rojo you might like to try Opera. Currently I have 165 windows open, which for me is a fairly small number (300 isn't so unusual). Opera will use a lot of memory, but it's fine in terms of performance, especially with the latest version.

Rojo

Bye

belisarius

bye

rcollyer

Apparently, Gaming is the one to beat. 18 of their users have founder badges. We need more of our people to log into Area 51 to claim their badges. We can beat 18, I'm sure of it.

Rojo

@OleksandrR. I might try it

Sjoerd C. de Vries

@OleksandrR. Hi. With that many tabs, how do you differentiate between them? Can't be that big.

Oleksandr R.

02:57

@SjoerdC.deVries the tab metaphor completely breaks down. I disabled the tab bar. Opera has other mechanisms for selecting documents.

Rojo

Brb, I'm gonna restart this

@belisarius You're the first one I know that used it. Nice to know that

Oleksandr R.

Personally I never liked the tab metaphor at all, precisely for the reason you mention.

Sjoerd C. de Vries

@rcollyer I thought I would get the founder badge on my mma profile, but it's in the area51 profile ;(

rcollyer

@SjoerdC.deVries Yeah, that sucks. I wonder if we can convince the powers that be that it needs to be on the launched site...

Oleksandr R.

Okay, I should go to bed. Night all!

rcollyer

03:01

Night.

My turn. Bye all.

Sjoerd C. de Vries

Night. Me too

Rojo

Night

..

Night

..

Night

I feel spammy

Rojo

03:21

@R.M try {x, x = 7; x} and enjoy the result :P

R.M

03:40

@Rojo what?

Rojo

{x,7}

Rojo

04:31

@belisarius I'm not sure I understood if your comment was a "that would be nice" or a "I don't like that"

belisarius

@Rojo Beer has its downsides

What comment?

Rojo

@belisarius The side that you put on the table is the downside

The one on your Exclusions question

belisarius

@Rojo I posted two comments in a row

Rojo

" I'm sure if I understand your proposal, but I don't like my approach because f[x_]:= 10^6 IntegerPart[x] and f[x_]:= 10^6 x should give different results"

That was the one for me

"Interesting point detection routine" sounds out of my reach

belisarius

@Rojo Look at the image

Plot[] explores discontinuities on its own

Rojo

04:35

Interesting

belisarius

for some reason, it is not finding the discontinuities in f'

I don't know why

Rojo

@belisarius test this

h[i_?NumericQ] := UnitStep[i]

Plot[{h[t], 2 UnitStep[t - 1]}, {t, -2, 2}, PlotStyle -> Thick]

From that, I don't think Plot finds the discontinuities with that routine

It must be symbolic preprocessing

Right?

belisarius

@Rojo test this

l = {5, 6, 6, 5, 6, 6, 5};
f = Interpolation@l;
g[t_?NumericQ] = D[f[t], t];
data = Reap[
Plot[ g@x, {x, 1, 7}, EvaluationMonitor :> Sow[{x, g[x]}]] ][[-1,
1]];
ListPlot[data , Filling -> Axis]

Rojo

Yeah

belisarius

So?

Rojo

04:43

Well, it samples more points in the discontinuities

but still, it doesn't seem to detect them for the purposes of excluding them

or to detect them at all

belisarius

nono, it is sampling because it detects a discontinuity

and tracks it down to see if it can plot it or needs to exclude it

... and arrives to the wrong conclusion ... why?

Rojo

How are you sure of that?

belisarius

@Rojo At this time I'm pretty unsure of everything

Rojo

I mean, that it's not simply some recursive division of the domain in parts, giving more points to the parts with bigger jumps between contiguous samples?

belisarius

@Rojo that is the same dog, just different rope

Rojo

04:47

Well, no

because it isn't detecting discontinuities first

Just sampling where it needs more points, without ever caring to decide if there's a discontinuity, or anything

In the example I gave you, you see that the very same function (UnitStep) has its jump excluded when its symbolic, but not when it's numeric

At least it can't only be that algorithm what detects exclusions

belisarius

I see ... your bet is that Mma is unable to exclude on numerically defined functions

Rojo

Yeah

belisarius

let me see if I can find some counter example

@Rojo NumericQ seems to inhibit the exclusions, yes

Rojo

@belisarius If you had to find the discontinuities of a symbolic expression

how would you do it? Any good MMA function for that that may be what Plot uses?

belisarius

@Rojo Limit is enough

but you have to guess the disc point

Rojo

04:57

Right...

belisarius

or you may check the convergence radius of the series expansion

Anyway, too tired now. Need some sleep

@Rojo Good night!

Rojo

@belisarius Night!

Mr.Wizard

07:51

@Rojo Currently at 252 myself. Since they added that Panorama thing to Firefox I never seem to close tabs, I just move them around a lot. :o)

Szabolcs

09:57

Does anyone know how I can open a palette from the Palettes menu programmatically so that the "PalettesMenuSettings" will be preserved?

2

Q: Programmatically opening a palette from the Palettes menu

How can I programmatically open a palette from the Palettes menu? Is there a Front End token for this? Motivation: Certain settings for the palettes that are installed into standard locations and show up in the Palettes menu are stored in the "PalettesMenuSettings" global option (accessible ...

front-end palettes

Actually belisarius's comment answers it. I missed the correct token yesterday.

Szabolcs

10:15

Any Mac users around? @R.M?

What does a MessageDialog look like on Mac? Is it that "rolling down" sheet or an independent window?

Szabolcs

11:04

Can anyone try evaluating the following? Import["https://github.com/downloads/szhorvat/SEUploader/SE%20Uploader.nb", "String"]

It gives an error for me, but my web browser does manage to download it.

J. M.

"For HTTPS connections, you might need to inspect the authenticity of the server's SSL certificate and choose to accept it." - if only I knew how to do it within Mathematica...

Szabolcs

:( why oh why oh why does github have to force https for downloads???

really have to find alternative file hosting

J. M.

@Szabolcs Paranoia?

Szabolcs

@J.M. What happens if you remove the s?

just use http, for downloads it should work (just tried)

J. M.

I'm still getting a FetchURL::conopen error within Mathematica. Odd, since I can download images from within Mathematica...

Szabolcs

11:14

@J.M. I think the problem is the space in the name, but I am not sure how to work around it.

Other than upload a file with no spaces in the name.

J. M.

@Szabolcs Well, how about a different separator, like a dash?

Szabolcs

Yes, I'll need to do that.

@J.M. Are you still going to be around for 15 minutes more? I'd really like you to test something :-)

J. M.

I won't be leaving until 40 minutes, so sure. :)

Szabolcs

@J.M. Do you have the image uploader palette installed?

J. M.

Apparently, not on this computer. Wait...

Szabolcs

11:25

@J.M. Can you install it using the instructions here? --> meta.mathematica.stackexchange.com/a/32/12

Let me know if there was something in the installation instructions that was not clear.

J. M.

I'm on Ubuntu, so I had to un-hide the directory where the palette has to be, but otherwise, it seems clear. (I don't know what's the directory structure in Windows nowadays, so I can't say anything about it...)

Szabolcs

@J.M. Okay, so you got the palette in the palettes menu now?

J. M.

Yep.

Szabolcs

@J.M. Does the Update button work?

It should tell you that there are no updates right now.

J. M.

@Szabolcs I get the Version Information dialog box.

Szabolcs

11:34

@J.M. Does it say that both the online and local versions are 102?

J. M.

Yep.

Szabolcs

@J.M. Could you try again please?

I really hope the updating will go smoothly.

@J.M. Did it work ... ?

J. M.

Wait, I'm about to click on the "Update to new version" button...

Well, the update worked nicely. It's now the 103 version.

Szabolcs

Phew ...

I'm really happy. :-)

@J.M. One final question: does this work, or does it also complain about HTTPS problems? --> Import["https://raw.github.com/szhorvat/SEUploader/master/ImageUploader.m", "String"]

J. M.

On the other hand, it might be a good idea to give feedback that the Markdown has been successfully copied to the Clipboard...

@Szabolcs That worked, I see the content of the package file.

Szabolcs

11:46

@J.M. If it's not copied successfully, it does give feedback

J. M.

Hmm, okay.

Szabolcs

@J.M. The upload dialog should disappear only when the upload has finished, that should give an indication of how long it takes.

J. M.

Yes, I tried it just now on a more complicated image.

Szabolcs

@J.M. One more update pushed, can you test once more please? Then I'm leaving.

R Hall

12:02

@Szabolcs It works but complains about SSL Certificate

Szabolcs

@RHall Are you on Linux?

R Hall

@Szabolcs Mac OSX 10.8

Szabolcs

@RHall Can you please try Import["https://raw.github.com/szhorvat/SEUploader/master/SEUploaderLatest.nb", "String"]? Does it also complain? What about Import["https://raw.github.com/szhorvat/SEUploader/master/version"]?

J. M.

@Szabolcs It works.

R Hall

@Szabolcs it works with the same SSL warnings.

Szabolcs

12:05

@RHall Hmmm ... I'll look into that when I come back. Need to go now. I guess in the worst case I can Quiet the specific warning. Can you post what it is exactly, including the message name? (I don't get it on Windows.)

R Hall

@Szabolcs Yea it's a system message and since I'm on the developers version of 10.8 I can not legally post it yet. Easy to note that you need to answer it though and everything after that runs clean.

J. M.

@RHall version 10, huh?

Szabolcs

@J.M. of OS X, not Mathematica

If it's a system message I can't Quiet it anyway

R Hall

@Szabolcs Mountain Lion 10.8 current is 10.7

@J.M. Still waiting for MMA 9 like the rest of us though ;)

J. M.

@Szabolcs Ah. I was about to ask how one gets two versions ahead... :D

belisarius

17:37

@J.M. Shhhh

acl

19:31

I had written an answer for this question, but changed my mind and erased all the text, links, etc. Now, if I try to close the window, I'm asked "Are you sure you want to leave this page? You have started writing or editing a post.", even though I've erased all the text

If I close the tab and then reopen the page, the erased text is still there.

This isn't a problem but I am curious: suppose I want to get rid of the text completely and never see it again. How could I do that?

@OleksandrR. but why not store them as bookmarks? I have my bookmarks indexable and accessible by typing a few characters and pressing return, systemwide. Or is there some reason you need them actually open?

belisarius

@acl Hey ! I want to see your answer!

:)

R.M

@acl you should see a "discard" link somewhere close to the submit button

acl

@R.M ah, I missed that. stupid! thanks

@belisarius if I get some time to finish it I'll post it, but don't imagine any revelations...

belisarius

19:48

@acl It is tightly related to a very good answer of yours. So, yes, I've high expectations

14

A: A curious Plot with IntegerPart[x]

I've completely overhauled my answer. I believe this now answers the questions posed (why mma thinks the violet line is the derivative of IntegerPart'[x]). Let's first look at ND, simply because its internals are easier to access and we may obtain some insight. Try: Needs["NumericalCalculus`"] ...

acl

@belisarius yes well at that time I was less busy. this period things are too hectic... (and any downtime is invested into beer-drinking)

belisarius

@acl As in "I spent a lot of money in beer and women, and wasted the rest"

2

acl

@belisarius right...

belisarius

@R.M Thanks for the edit. I liked the " " in the title though ...

Rojo

20:04

@belisarius, the FindCounterExample will be a 3x1

belisarius

@Rojo ?

Rojo

FindProof and Prove probably have the same syntax,

belisarius

ahh .. ok

Rojo

and I think that Prove calls first FindCounterexample

and if it fails, tries with Find Prove

TraceInternal shows a lot. Let's see if something is understandable

belisarius

@Rojo Feel free to edit the question if you want

damn repcap

Rojo

20:07

@belisarius Capped already?

belisarius

@Rojo yep

Rojo

Nice

I'll go upvote some of your stuff

belisarius

mathematica.stackexchange.com/…

@Rojo Sadistic impulses on Sunday?

R.M

@belisarius oh. I thought you were trying to indicate that it's a function using that instead of backticks...

Rojo

@belisarius Hehe

I haven't capped since 1st july it seems

I'm on a low rep streak

July 7 my last >100

belisarius

20:09

@R.M Nope, but the name of the function is so large that I thought the title was clearer with apostrophes

R.M

I'm 100 away from 20k... then I can rest

belisarius

@R.M yeah you may let the hypnotoad to hibernate

Rojo

20:49

@belisarius Does it tell you anything that the first argument are the "goals" and the second the "axioms"?

and the third argument probably is some kind of integer specifying "how much it searchs for a counterexample", that defaults to Infinity in which case I got no clue what it means

It uses FindInstance

belisarius

@Rojo Let me think about it

@Rojo EquationalLogic`FindCounterexample[Tan[y/x] == 1, 1 == x^2 + y^2]

returns 100

while

EquationalLogic`FindCounterexample[x == y, 1 == x^2 + y^2]

returns 31

does not make much sense

Rojo

21:11

@belisarius Do EquationLogic`FindProof[x == 0, x == 0]

belisarius

nice!

Rojo

We are getting somewhere

belisarius

EquationalLogic`FindProof[x x + y y == 2 x x , x == y]

mmm

Rojo

It's probably a work in progress

belisarius

Well, they can prove that x==0 if x==0. That is something :)

Rojo

21:17

Hehe

Still need to work on FindProof[2 x == 2 y, x == y]

belisarius

EquationalLogic`FindProof[x + x == 2 , x == 1]

fails

@Rojo Hey!

EquationalLogic`FindProof[ x == y , x == 1 && y == 1]

great!

Rojo

Wow

That's smart!

belisarius

21:33

@Rojo EquationalLogic`FindProof[x == 1, x == 1 && x == 2]

Rojo

OMG

Well

Your axioms are insane already

:P

Your fault

belisarius

as always

belisarius

22:50

@Rojo Found a thing in the trace named skolemconst$

Skolem normal form

Reduction to Skolem normal form is a method for removing existential quantifiers from formal logic statements, often performed as the first step in an automated theorem prover. A formula of first-order logic is in Skolem normal form (named after Thoralf Skolem) if it is in conjunctive prenex normal form with only universal first-order quantifiers. Every first-order formula can be converted into Skolem normal form while not changing its satisfiability via a process called Skolemization (sometimes spelled "Skolemnization"). The resulting formula is not necessarily equivalent to the original...

Transcript for