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[WSG21] Daily Study Group: Wolfram Language Basics

POSTED BY: Abrita Chakravarty
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Dear Dr. Lippolt,

All your solutions were accepted during manual grading of the exercises. We faced some issues with the auto-grader accepting alternate solutions to some of the problems. Our apologies for the inconvenience.

POSTED BY: Abrita Chakravarty
Peter Lippolt
Peter Lippolt
Posted 4 years ago
POSTED BY: Peter Lippolt
Peter Lippolt
Peter Lippolt
Posted 4 years ago
POSTED BY: Peter Lippolt

Hello,

I'm just re-reading and executing the notebook codes. Again, what an abundance of inspiring examples! Thanks :-)

Arpad
POSTED BY: Arpad Foldesi

I have a similar problem starting with first question. I used a shorthand notation of Part without "Part" that produced the requested elements from the question, but was marked wrong by auto-grader.

I'll keep working on the exercises.
POSTED BY: Michael Lyda

My delivery issue appears to be an issue with the email address string from a copy paste. It appears resolved.
POSTED BY: Paul Erickson

This is an automatically generated Delivery Status Notification.

Delivery to the following recipients failed permanently:

  • "wolfram-u@wolfram.com wolfram-u"@wolfram.com

Reason: Permanent Error

I was having trouble with auto grader on 7 problems. I was trying to submit a nb file with the solutions.
POSTED BY: Paul Erickson

Hi Fedor,

  1. The email address wolfram-u@wolfram.com is able to receive emails with attachments from all our users. We have not run into this issue before. We'll check again and keep you posted.
  2. Folks have until March 19 to complete the quizzes and exercises. We'll tally up the scores after that and send you notification via email.
  3. To continue the never-ending quest for knowledge? :)
POSTED BY: Abrita Chakravarty

Good day, everyone.

I completed the exams notebook (not all of it, if we are to believe the results of the "Check" button). Earlier I was advised to submit the notebook via email. However, when I try to, I get the "Client host rejected: Your message was rejected due to spam filtering. Please see http://www.sophos.com/security/ip-lookup..." mail send error.

So, the questions I'd like you to assist me with are the following. Are there any other ways to submit the notebook? How do I know, if and when all the results (quizes and exams) are recieved and are ok (or not)? What does humanity exist for? The last question is optional.
POSTED BY: Fedor Sumkin
POSTED BY: Andreas Rudolph
lara wag
lara wag
Posted 4 years ago

My local installation of 2.17 works with my solution also without errors. However, in the cloud I get a completely different error message than Andreas. (@Andreas I put the entries in ChemicalData["name","property"] in different order, please see the reference.)

Maybe "my error message" is because I pasted the image directly into my solution? - But: How else?

Attachment

Attachments:
errorMessage2-17.png
POSTED BY: lara wag

Hi larawag NN

as by instructions "Use "MoleculeRecognize" to identify the molecule in the following image....".

In my first line, I write " molec = MoleculeRecognize [paste here the given picture]".

If I paste just this first line into the "exercise notebook" (observe in the first lines that these seem to be local copies) and run it, he replies with "MoleculeRecognize" is not currently supported in the Wolfram Cloud". The rest of the messages from "ChemicalData" etc are just follow-on problems, as "molec" already fails.

BR, Andreasenter image description here
POSTED BY: Andreas Rudolph

Hi Andreas and Larawag,

I have noticed the issues with both the questions using images. I have come to a similar conclusion as you both. Although your image processing code runs just fine on your local installations, the autograder seems to be running into an issue with the same code snippet in a cloud sandbox. We are looking into it. Hopefully we'll have a resolution soon. And as you have quoted, we do have the backup option of emailing the notebook. Thanks everyone for your patience as we work through these issues.

Best, Abrita
POSTED BY: Abrita Chakravarty

Facing hurdle adding images to the notebook. Here is the original thread that I posted: https://community.wolfram.com/groups/-/m/t/2211885?ppauth=P83yUOh1
POSTED BY: Rajeev Bagra

Hi Rajeev,

For the purposes of this particular study group I would encourage you to use Wolfram|One and the regular Wolfram notebook which offers some more flexibility in adding different types of content (text, code or images) to the notebook. You will have more freedom to write your own code in the Wolfram Language in this notebook. And to add images you can simply copy and paste them into your notebook.

The Wolfram Alpha Notebook Edition is intended for slightly different use--to enable users to provide free-form input to get instant answers to questions, create and customize graphs, and also add their own notes in text.

Please let us know or feel free to contact our support team if you have further questions about which product will best suit your needs and expectations. Thanks
POSTED BY: Abrita Chakravarty

Tried Wolfram Notebook (https://develop.wolframcloud.com/env/286fe86b-1d85-4150-8150-abfd773e80d7) by drag & drop, CtrlC + CtrlV, and copy/paste options. No way I could insert image. No option to upload image from desktop despite this message after clicking enter image description hereInsert Image:

Insert Image Drag and drop an image from the desktop into your notebook, or use Import to import an image from file.
POSTED BY: Rajeev Bagra

Good day, everyone.

Being a russian, I'd like to point out, that we have 10 vowels in our alphabet: а, я, о, ё, ы, и, э, е, у, ю. I can solve exercise 2.11 of the exam the way you want me to, but that'd be wrong.
POSTED BY: Fedor Sumkin

Hi Fedor,

Thank you for your feedback. We have made note of the issue. For this specific exercise, we will rephrase the question as follows:

Make a list of the letters in the Russian Alphabet, with the five letters {а,е,и,о,у} in Style Red. (Hint: Use ReplaceAll and string pattern matching with StringMatchQ. Restrict the match to be a String before trying to match it against the letters {а,е,и,о,у}.)
POSTED BY: Abrita Chakravarty

Hi Everyone, I understand you have been running into some issues with the autograder. If your solution is generating the same output as shown in the expected output and you are satisfied with all your code, please download a copy of the exercise notebook and email it to us wolfram-u@wolfram.com.

You will find the exercise notebook in the "Copied Files" directory among your cloud files. It should appear as "02_exercise.nb"

enter image description here
POSTED BY: Abrita Chakravarty

In 2.13. I have the correct result with some sytax error that I do not understand what it means. My answer cannot be evaluated as correct.

In 2.17 also the correct answer cannot be evaluated as correct.

enter image description here
POSTED BY: Artin Hatzikioseyian

Are there more statements involved when you developed the answer, which perhaps are required to also be copied to the answer field?
POSTED BY: John Burgers
Peter Lippolt
Peter Lippolt
Posted 4 years ago

No fun ! Not sure, who should try again ...

enter image description here

@Fedor Sumkin: your Complement approach is more elegant!
POSTED BY: Peter Lippolt

Hi Everyone, I'm not having luck with the autograder input box. I've read Abrita's note above that a complete statement, or compound statement, including any definitions, is needed. For example exercise 2.3 I got the same statement in a practice notebook were the statement==answer yields true, copied the statement to the grader box where it says "try again". I think it was Abrida who said in this cases to log on to the Wolfram account - my files - copied files folder and email you a download. Is that the procedure ? Can you remind me, or post, the email addresses we can send to? Thank you John.
POSTED BY: John Burgers

Good day, everyone!

I just don't understand how my solution is not right. I tried different implementations and re-checked many times. Please, assist me, what it wrong?

enter image description here
POSTED BY: Fedor Sumkin
Doug Beveridge
Doug Beveridge
Posted 4 years ago

I get the same result , I think the auto-grader is not picking up the right solutions

Similarly 12.2 solution correct but rejected .

12.3 solution correct but get an error "ToExpression::sntxi : Incomplete expression; more input is needed"

POSTED BY: Doug Beveridge
POSTED BY: Andreas Rudolph

Have you checked that your solution does not include unwanted "blanks"? I typically work with my local Mathematica, and copy paste finished solutions over into the examination notebook. For some solutions he shows me a "try again". If I remove all excess blanks directly in the examination notebook it sometimes works. Your "vowel" string appears to be a bit suspicious. (just an idea)
POSTED BY: Andreas Rudolph
Doug Beveridge
Doug Beveridge
Posted 4 years ago

Andries Do you get a solution to work with Ex 2.3 . What operating system are you using. I am using Windows 10.

I have followed your advice and removed all blanks and created my vowels and consonants using Alphabet[] but still no joy.
POSTED BY: Doug Beveridge

Hi Fedor, Please feel free to send your exercise notebook with all the solutions to wolfram-u@wolfram.com. Your solution looks fine.

POSTED BY: Abrita Chakravarty
Gustavo Raush
Gustavo Raush
Posted 4 years ago

Dear Abrita,

Since I experience the same validation problem commented on in the thread. Can you give me instructions on how to download the "WSG: Wolfram Language Basics | Level I Certification" notebook to be conveniently fulfilled and emailed to wolfram-u@wolfram.com? I only see a web page without download options how I could see in Wolfram|One.

Best regards Gustavo
POSTED BY: Gustavo Raush
Doug Beveridge
Doug Beveridge
Posted 4 years ago

I think there could be an error in question 2.5 of the exercises

"starting from n=0 to n=4"

should be "starting from n=0 to n=5 "

Please give that email address so we can query solutions to the auto-grader.
POSTED BY: Doug Beveridge

Hi Doug,

Remember

NestGraph[f,expr,n]

gives the graph obtained by starting with expr and applying f successively n times. So if you want the final output to be the result of applying f on the values say 0,1, and 2 you will need to nest it 3 times.
POSTED BY: Abrita Chakravarty
Doug Beveridge
Doug Beveridge
Posted 4 years ago

I used an expression in the form of

NestGraph[f , 0 , 5]

and produced the graph and was accepted by the autograder .

POSTED BY: Doug Beveridge
Michael Hobbs
Michael Hobbs
Posted 4 years ago

Hi, and thank you for all you excellent teaching.

I've just written three answers (all of which gave the expected outcome), for 2.1 in the level 1 exercises. All were rejected by the check answers button.

Thanks for any help you may give. Michael
POSTED BY: Michael Hobbs

I just want to point out that when you send your solution to the autograder (by clicking on the "Check Solution" button) it does not have access to any definitions you may have created in the exercise notebook itself. So you will have to include that definition as part of your solution. 

myList = {1,2,3,4};
Part[myList,2]

or

myList = {1,2,3,4};
myList[[2]]
POSTED BY: Abrita Chakravarty
Michael Hobbs
Michael Hobbs
Posted 4 years ago

Thank you Abrita, that has resolved the problem.
POSTED BY: Michael Hobbs

Call me crazy, I work with Mathematica on a 60 inch Samsung monitor. I'd like some guidance on how to reset Mathematica defaults (window size, text size ) when opening new sessions and work books. Could all the adjustments be made in the Option inspector? Currently I use Cntrl- mouse scroll to adjust the text inside the notebook to a reasonable size, which has not effect on the Window Title and tool bar. Thanks in advance for any help or pointing me to further reading.

Great job Arben and Abrita, the course surprised me in how much I picked up, and by it's breadth. Exciting ride keeping up with the pace. John
POSTED BY: John Burgers

Hi John, Glad to know you found the series helpful.

To set the text size one option is to set the Magnification for Global Preferences from the Options Inspector. I have mine set to 1.5 and its helpful even on a small screen. You will find detailed instructions here: https://support.wolfram.com/25214. This will enlarge all content in all notebooks. I believe the same approach should work for setting the WindowSize as well.

POSTED BY: Abrita Chakravarty
Rongoetz
Rongoetz
Posted 4 years ago

I hate to bring this up, but in Quiz 2, problem 6 begins with the ungrammatical phrase "Which pure function takes a two inputs..." Clearly something is wrong here: I could delete the word "a" and get one answer, but if I imagine that the the question has missing words then I can easily find two words that would change my answer. I'm going with the choice of deleting the word "a", but thought you might want to fix the question at some point.
POSTED BY: Rongoetz

The correct text of the question should be: "Which pure function takes two inputs and returns a list of their sum, difference and product?"

We're working on updating the quiz itself. Thank you for reporting the issue.
POSTED BY: Abrita Chakravarty
Doug Beveridge
Doug Beveridge
Posted 4 years ago

What is the email to query the exercises that are not marked correct by the auto grader? Can we just send the code for the specific question?

POSTED BY: Doug Beveridge

Hi Doug, We would like to request you to download the entire exercise notebook with your final solutions and email it to wolfram-u@wolfram.com
POSTED BY: Abrita Chakravarty

Commenting further on the post of larawag NN how can arbitrary precision 10 be better and more accurate than MachinePrecision which is almost 16 (15.9546) ?
POSTED BY: Artin Hatzikioseyian
lara wag
lara wag
Posted 4 years ago

Abrita, thank you very much for yesterday's very interesting and enlightening lesson.

On slide 14 of "Tips and Tricks" an example was shown regarding machine precision and arbitrary precision. Is there any way that WL's output will indicate when the machine precision solution will be wrong?

If one doesn't have a hint that the solution is wrong, one could be lulled into a false sense of security and thus assume wrong results to be correct. Especially since the command N[...] is more intuitive for a user than N[..., 10], where the latter command provides the more accurate result, see attachment.

As a side topic: Using Mathematica, how can you prove (or confirm otherwise) which of the two results is the correct one?

I attached a picture of your example, which I have adapted a bit to make this issue a clearer. After playing around for a while, I found the a illustration which shows roughly where the solution breaks down. This point seems to be independent of the number of valid digits (here the n-digit precision was set to n=10), and so, it originates from the first term (term with machine precision), right?

Attachment

Attachment

Attachments:
excerpt.png
listPlot.png
POSTED BY: lara wag
POSTED BY: Artin Hatzikioseyian
POSTED BY: Abrita Chakravarty
POSTED BY: Artin Hatzikioseyian
Corina Murg
Corina Murg
Posted 4 years ago

Hello, I created an app with 3 sliders, and I'm trying to position all three vertically and next to each other. Right now I only know how to place them vertically, with the 2nd and 3rd underneath the previous one. Thank you in advance for your help.

Corina
POSTED BY: Corina Murg

You could use Grid or Column as shown in this example at http://reference.wolfram.com/language/ref/Slider.html

POSTED BY: Abrita Chakravarty
Attachments:
Stylesheet Working.nb
Stylesheet Working.pdf
POSTED BY: Hee-Young Shin
POSTED BY: Abrita Chakravarty

Try as I may the statement below to combine a video and audio into a video file didn't work for me. I gave up looking for help under Export to dissect the use of "Animation" , "Audio" ...

Export["sineManipulate3.mp4", {"Animation" -> 
   Manipulate[
    Plot[Sin[k x], {x, 0, 2 \[Pi]}, 
     PlotRange -> {-1, 1}], {{k, .1, "Wavenumber"}, .1, 5}], 
  "Audio" -> sufjanSong}, "Rules"]

Also got this error message which I couldn't understand or work with, Export::interr2: An unknown internal error occurred. Consult Internal`$LastInternalFailure for potential information.

Thanks in advance for any insight on where to look for assistance, John
POSTED BY: John Burgers
POSTED BY: Arben Kalziqi
POSTED BY: John Burgers
Ulf Schmidt
Ulf Schmidt
Posted 4 years ago 
Import["hoffmann_ohno.mp4", "FrameCount"]

626

vid = Video["hoffmann_ohno.mp4"]; vidFrames = VideoExtractFrames[vid, All];

Length[vidFrames]

627

Are there 626 frames or 627 frames?
POSTED BY: Ulf Schmidt

Hi Ron, Sure, I see where you are coming from. This really is a very specific use-case for Alternatives and if you are used to setting up Alternatives (as logical OR) for things like pattern-matching, the way it is used in Element can appear non-intuitive.

About your suggestion for extending SubsetQ to regions and domains, we'll be happy to forward it to the development team.
POSTED BY: Abrita Chakravarty
POSTED BY: Abrita Chakravarty
Updating Name
Updating Name
Posted 4 years ago

Abrita,

Thanks for the reply. I understand how Element is working, but not why. My question simplifies to: How am I supposed to understand that the syntax (x1 | x2 | x3 | x4) \[Element] Reals means the same as (x1 \[Element] Reals) \[And] (x2 \[Element] Reals) \[And] (x3 \[Element] Reals) \[And] (x4 \[Element] Reals)? Is that something I should be able to work out if I really understood Alternatives? Are there other areas where Alternatives is used like this?

My question about SubsetQ and related functions: I know they are intended for lists, I just think that it might be time for them to be extended to the more complicated classes of sets that have been implemented in the Wolfram Language lately (Region as well as the various domains). I'm guessing that's not an easy thing to do, but I can dream, right?

Thanks, Ron
POSTED BY: Updating Name
Rongoetz
Rongoetz
Posted 4 years ago
POSTED BY: Rongoetz

Note to File : Working with Data
Slide 10 of 21 Visualise the total sales for each title: RotateLeft[ ... ] shifts the labels one to the left of the correct sales bar.

John Burgers
POSTED BY: John Burgers

Thank you for reporting the error. Not sure why RotateLeft crept in there. It should simply be:

BarChart[data2[[All, 2]], ChartLabels -> Placed[data2[[All, 1]], Below, Rotate[#, Pi/2] &]]

The idea was to rotate the labels by 90 degrees to avoid crowding at the bottom of the chart.
POSTED BY: Abrita Chakravarty
Rongoetz
Rongoetz
Posted 4 years ago
POSTED BY: Rongoetz
Updating Name
Updating Name
Posted 4 years ago

I figured it out.

someText = {"State A", "State A1", "State A2", "State B", "Random Test"};
stringToAction[x_] := Switch[x
   , Condition[x, StringMatchQ[x, "State A*"]], actionA
   , "State B", actionB
   , _, "State Unrecognized" <> x
   ];
Map[stringToAction, someText]
POSTED BY: Updating Name
Rohit Namjoshi
Rohit Namjoshi
Posted 4 years ago

What about this input? Are there never multiple B states?

someText = {"State A", "State A1", "State A2", "State B1", "Random Test"};
POSTED BY: Rohit Namjoshi
Rohit Namjoshi
Rohit Namjoshi
Posted 4 years ago

Getting there .... :-)

someText = {"State A", "State A1", "State A2", "State B", "Random Test"};

stringToAction[string_] :=
 Which[
  StringMatchQ[string, "State A*"],
  "actionA",
  StringMatchQ[string, "State B*"],
  "actionB",
  True,
  "State Unrecognized: " <> string]

stringToAction /@ someText
(* {"actionA", "actionA", "actionA", "actionB", "State Unrecognized: Random Test"} *)

stringToAction2[string_] :=
 Switch[
  StringCases[string, "State " ~~ x_ ~~ ___ :> x],
  {"A"}, "actionA",
  {"B"}, "actionB",
  _, "State Unrecognized: " <> string]

stringToAction2 /@ someText
(* {"actionA", "actionA", "actionA", "actionB", "State Unrecognized: Random Test"} *)

If you have to deal with more than a handful of states and actions, rather than generating a long Switch or Which manually, considering using a list of rules and maybe Dispatch.
POSTED BY: Rohit Namjoshi
Rohit Namjoshi
Rohit Namjoshi
Posted 4 years ago

Hi John,

I would use Which rather than Switch for this

string = "State A2"

Which[
 string == "State A1",
 Print[string],
 string == "State A2",
 Print[StringReverse@string],
 string == "State A",
 Print[string]]
(* 2A etatS *)

Using Switch

Switch[string,
 "State A1",
 Print["State A1"],
 "State A2",
 Print["State A2"],
 "State A",
 Print["State A"]]
POSTED BY: Rohit Namjoshi
POSTED BY: John Hoffman
Rohit Namjoshi
Rohit Namjoshi
Posted 4 years ago

You are right, I completely misunderstood the question. Sorry about that.

The body of a pure function that does not use Function must end in &.

StringMatchQ[#, "State A*"] & /@ {"State A1", "State Ab", "State A1 zz", "State a"}
(* {True, True, True, False} *)
POSTED BY: Rohit Namjoshi

Rohit, you again misunderstood the issue. The issue is to put this into the switch statement. Here I take your answer, and put it into the switch statement. It fails. (In my original test on my notebook, I had the &, I just missed it when I typed it in here. This time I copied/pasted.) The first three entries in the output list should be "actionA" but they are all unrecognized by the switch statement.

someText = {"State A", "State A1", "State A2", "State B", "Random Test"};
stringToAction[x_] := Switch[x
   , StringMatchQ[#, "State A*"] &, actionA
   , "State B", actionB
   , _, "State Unrecognized" <> x
   ];
Map[stringToAction, someText]

{"State UnrecognizedState A", "State UnrecognizedState A1", "State UnrecognizedState A2", actionB, "State UnrecognizedRandom Test"}
POSTED BY: John Hoffman
POSTED BY: John Hoffman
POSTED BY: Abrita Chakravarty
POSTED BY: John Burgers
POSTED BY: Abrita Chakravarty

Thank-you Abrita. Explained very well. John
POSTED BY: John Burgers

Hello everyone! I was doing the exercises of the seventh session but I can't find the file "weather.dat". Could you please share it? Thanks in advance.
POSTED BY: Angel Mosquera

Hi Angel, I added weather.dat to the data folder. Sorry about that.
POSTED BY: Abrita Chakravarty

Thanks!!!!
POSTED BY: Angel Mosquera

Hi Abrita,

There are minor typos in the 2nd quiz that I would like to draw your attention:

  1. Problem 3 C) NIntegrate[f[n], {n, 0, 1}]. The last closing square bracket is missing;

  2. Problem 8 "Which is these functions ---?" -> "Which one of the following functions ---- ?" or simply "Which function ----?"

Thanks.
POSTED BY: Hee-Young Shin

Thank you. Sorry about that - we'll get these edited.
POSTED BY: Abrita Chakravarty

Hi Arben, see code snippet attached. Question why I didn't see an order of magnitude faster timing. John

Attachments:
05 Numerics Pack...nb
POSTED BY: John Burgers

Hi John,

Thanks for the notebook. My suspicion is that Accumulate is packing the array automatically—if it is packable—and that Accumulate was updated some time between the creation date of this original notebook and the present. See the linked notebook, where I change a 0 to a 0. to preclude the possibility of packing, and get (suspiciously...) a 10x slowdown. I can't be sure that that's because the array is no longer "packable", but that's my best guess.

I've asked through an internal channel for some clarification on this, and will update you if I learn anything!

https://www.wolframcloud.com/obj/arbenk/Published/05%20Numerics%20PackArray%20Timing%20(test).nb
POSTED BY: Arben Kalziqi

That was clever Arben, and teaches me how to diagnose. Thanks for asking forward. John
POSTED BY: John Burgers
Ulf Schmidt
Ulf Schmidt
Posted 4 years ago
POSTED BY: Ulf Schmidt
POSTED BY: Abrita Chakravarty
Attachments:
05 Numerics Pack...nb
POSTED BY: John Burgers
POSTED BY: Abrita Chakravarty
POSTED BY: Jamie Peterson

When will the Advanced Programming recording become available to rewatch?
POSTED BY: Steph Macurdy

Yesterday's Study Group recording is now available: https://wolfr.am/TyQ6Qt0q
POSTED BY: Jamie Peterson
POSTED BY: Fedor Sumkin
Ulf Schmidt
Ulf Schmidt
Posted 4 years ago 
sol = NDSolve[{f''[x] + f'[x] + 8 f[x] == 0, f[0] == 0, f'[0] == 1}, 
f, {x, 0, 10}] ;

Plot[Evaluate[f[x] /. sol], {x, 0, 10}, PlotRange -> All]

Expressions like Plot[Evaluate[f[x] /. sol] are given in the Help-examples of NDSolve

In the solution for Exercise 5.8 Plotting a result from NDSolve the following expression is given

Plot[f[x] /. sol, {x, 0, 10}, PlotRange -> All]

Both expressions give the same diagram.

In which cases i have to use Plot[Evaluate[f[x] /. sol] and in which cases i have to use Plot[f[x] /. sol] ?
POSTED BY: Ulf Schmidt
POSTED BY: Abrita Chakravarty
lara wag
lara wag
Posted 4 years ago
POSTED BY: lara wag

Hi Larawag,

I'm not sure that I understand what you're asking—if I do understand correctly, then that seems to work:

In[1]:= f[x_]:=2+Sin[x/a]
In[2]:= f[x]/.x/a->ξ
Out[2]:= 2+Sin[ξ]

Are you asking for something different? If so, could you provide an explicit sample input and the expected output?

Thanks!

Arben
POSTED BY: Arben Kalziqi
lara wag
lara wag
Posted 4 years ago
POSTED BY: lara wag

Hi larawag,

Ah, I see what you mean. That is indeed a difficult general problem to solve, and I've run into it myself in the past. After some searching, I've found something that seems to work... it still needs a bit of simplification (with Simplify or FullSimplify), but it ought to do what you want, and thee discussion surrounding it provides some insight as to why this is a nontrivial problem:

https://mathematica.stackexchange.com/questions/3822/can-i-simplify-an-expression-into-form-which-uses-my-own-definitions

Using: FullSimplify[expr // TermErsetzung[2 s == \[Xi] (-1 + s^2), s], Assumptions -> \[Xi] > 0] I was able to get pretty close to your desired output (really, just requiring breaking up the sum. Hopefully this is helpful!

Arben
POSTED BY: Arben Kalziqi
lara wag
lara wag
Posted 4 years ago

Thank you Arben for bringing this link to my attention (and of course for the quick and on-target reply...).

POSTED BY: lara wag

You're welcome, Larawag—glad to be able to help!

Arben
POSTED BY: Arben Kalziqi

Thanks Arben, The german term Ersetzung attacted me as I read German. That's a useful function. John.
POSTED BY: John Burgers
Fabio Alcaro
Fabio Alcaro
Posted 4 years ago

Good morning/evening,

In exercise 3.7 if I use the following code (in version 12.0) I generate the error General::ivar: -12.5659 is not a valid variable:

Manipulate[
 Plot[{Sin[x], Normal[Series[Sin[x], {x, 0, n}]]}, {x, -4 \[Pi], 
   4 \[Pi]}, PlotRange -> {-10, 10}], {n, 1, 23, 2}]

In order to fix it I have to force the evaluation of the series expansions as:

Manipulate[
 Plot[{Sin[x], 
   Normal[Series[Sin[x], {x, 0, n}]] // Evaluate}, {x, -4 \[Pi], 
   4 \[Pi]}, PlotRange -> {-10, 10}], {n, 1, 23, 2}]

Does anyobody experience the same? Most importantly, does anybody know why the first code snippet is not a valid Wolfram statement?

Thanks
POSTED BY: Fabio Alcaro
POSTED BY: Abrita Chakravarty
Fabio Alcaro
Fabio Alcaro
Posted 4 years ago

Thanks Abrita for the explanation!
POSTED BY: Fabio Alcaro
Updating Name
Updating Name
Posted 4 years ago

That was what I did, among other variations, but nothing worked in Chrome. I switched to a different browser and had no trouble. I'm guessing there is a way of telling Chrome it's OK to download DAT files, but I couldn't find it on a first pass through the settings.
POSTED BY: Updating Name
Rongoetz
Rongoetz
Posted 4 years ago

I can't seem to download the data1D.dat data1D2.dat files in the data folder.

POSTED BY: Rongoetz
POSTED BY: Abrita Chakravarty
Roger Shifrin
Roger Shifrin
Posted 4 years ago

Great talks by Abrita and Arben. How can I find my way to the quiz? Thanks, Roger
POSTED BY: Roger Shifrin

Hi Roger, The link to the quiz that was shared in the study group session today, will alsol be included in the next reminder email for the webinar.

POSTED BY: Abrita Chakravarty

May I get a link to the first session on Monday? I have the 2nd one from Tuesday and 3rd one from Thursday. Thank you
POSTED BY: Michael Lyda
POSTED BY: Abrita Chakravarty

Thanks Ron, for the catching the issue and sharing the resolution.
POSTED BY: Abrita Chakravarty
Rongoetz
Rongoetz
Posted 4 years ago

In slide 31 of the notebook for the second day, it looks like there is a small error in coding for the function FixMatrix. The code works fine for square matrices (as in the examples given), but not for general matrices, because the mapping over the column numbers is taken over the row numbers instead. It can be fixed by replacing 

Range[Length[mat]] (*the list of row numbers*)

by either 

Range[Length[Transpose[mat]]]

or 

Range[Last[Dimensions[mat]]] (*the list of column numbers*)

Ron Goetz
POSTED BY: Rongoetz

Good day, everyone!

I've got a small noobie question. I declare a function using Module to hide local variable x. And I expect x to be local. But when I check what is x with question mark, it is says, x is global.

Are things to be that way? What don't I understand?

enter image description here
POSTED BY: Fedor Sumkin

Hi Fedor, The syntax coloring is giving us a hint that the "?" is not working on the local symbol x but on the global symbol (since x appears black, not green). So it is correctly informing us of the status of the global "x". Perhaps you could try replacing "?x" with Information[x] which would ensure the right "x" was being used for information. enter image description here
POSTED BY: Abrita Chakravarty
Rohit Namjoshi
Rohit Namjoshi
Posted 4 years ago

Alternative for first 500 digits of π

N[Pi, 500] // RealDigits // First

While Table[Sin[x],{x,1,10}] and Plot[Sin[x],{x,1,10}] use the same x range, the points used by Plot are chosen so that the plot is "smooth".

tablePoints = Table[Sin[x], {x, 1, 10}];

plot = Plot[Sin[x], {x, 1, 10}];
plotPoints = Cases[plot, Line[p_] :> p, All] // First;

ListPlot[{plotPoints, tablePoints}, 
 PlotStyle -> {Automatic, Directive[PointSize[Medium], Red]}]

enter image description here
POSTED BY: Rohit Namjoshi
Updating Name
Updating Name
Posted 4 years ago

We ran into some issues with a couple of examples during today's session. Here are possible resolutions to those issues:

  • First 500 digits of Pi: ResourceFunction["NthDigit"][\[Pi], #] & /@ Range[500]
  • Example of using lists in the same way (domain of input values) in two different Wolfram Language functions: Table[Sin[x],{x,1,10}] and Plot[Sin[x],{x,1,10}]

Here is the example of processing the DNA sequence from the BRCA 1 gene (with the nucleotides as chemical entities instead of just string characters):

Counts[Characters[Entity["Gene", {"BRCA1",  {"Species" -> "HomoSapiens"}}]["ReferenceSequence"]] /. 
     {"A" -> Entity["Chemical", "Adenine"], 
      "T" ->  Entity["Chemical", "Thymine"], 
      "G" ->  Entity["Chemical", "Guanine"], 
      "C" -> Entity["Chemical", "Cytosine"]}]
POSTED BY: Updating Name
Rongoetz
Rongoetz
Posted 4 years ago

Thank you for showing the replacement to turn the strings into entities in the nucleotides example. Ron
POSTED BY: Rongoetz

For all the new folks who attended Study Group today: Feel free to try Wolfram One (https://www.wolfram.com/wolfram-one/) to open up the notebook we shared with you.
POSTED BY: Abrita Chakravarty
POSTED BY: Universal Simplexity
Updating Name
Updating Name
Posted 4 years ago

Unfortunately it appears that the free basic plan does not allow file upload or the option to download and install the Wolfram Desktop. You would have to subscribe to a paid plan for those options.

You could download and install a trial version of Mathematica to open the shared notebooks https://www.wolfram.com/mathematica/trial/
POSTED BY: Updating Name

Happy to be a part of this study session cohort!
POSTED BY: Steph Macurdy

The "Wolfram Language basics" study group begins today. See you there!
POSTED BY: Abrita Chakravarty
POSTED BY: Jamie Peterson
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