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RSS Feed for Wolfram Community showing any discussions in tag Mathematics sorted by active[CALL] Most common pitfalls for beginners of Wolfram Language
https://community.wolfram.com/groups/-/m/t/1070264
[Wolfram Language][1] (WL) is a powerful multi-paradigm programing language. There is a set of common mistakes that repeatedly tend to entrap new users. **This is a call to describe such mistakes building a "black-listing" guide for novice coders.** Please consider contributing. I suggest following simple rules (with gratitude adapted from a [similar effort][2]):
- One topic per answer
- Focus on non-advanced uses (it is intended to be useful for beginners and as a question closing reference)
- Include a self explanatory title in header style (example: "# Basic built-in function syntax"; see [syntax guide][3] )
- Explain the symptoms, the mechanism behind the scenes and all possible causes and solutions you can think of. Be sure to include a beginner's level explanation (and a more advance one too, if you can)
*Please, use "**Reply**" to a specific comment for structured clarity of nested comments.*
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## Table of Contents
- [Basic syntax of built-in functions][4]
- [Learn how to use the Documentation Center effectively][5]
- [Sorting numerical data and the behavior of Sort][6]
- [What does @#(%=<\[!} et cetera mean?][7]
- [Consider Reap/Sow Instead of AppendTo][8]
- [Alternatives to Reap/Sow][9]
- [Case sensitivity and typos][10]
- [Numerical vs Symbolic -- What to do when plots are blank][11]
- [Import and "CurrencyTokens"][12]
[1]: https://www.wolfram.com/language
[2]: https://mathematica.stackexchange.com/q/18393/13
[3]: http://community.wolfram.com/groups/-/m/t/270507
[4]: http://community.wolfram.com/groups/-/m/t/1069885
[5]: http://community.wolfram.com/groups/-/m/t/1070285
[6]: http://community.wolfram.com/groups/-/m/t/1070705
[7]: http://community.wolfram.com/groups/-/m/t/1070946
[8]: http://community.wolfram.com/groups/-/m/t/1084289
[9]: http://community.wolfram.com/groups/-/m/t/1164555
[10]: http://community.wolfram.com/groups/-/m/t/1084920
[11]: http://community.wolfram.com/groups/-/m/t/1086929
[12]: http://community.wolfram.com/groups/-/m/t/1086969Vitaliy Kaurov2017-04-23T23:54:23ZWhat is a quadratic matrix to the 0th power?
https://community.wolfram.com/groups/-/m/t/2130018
m^0 should be the [identity matrix][1]. but most of my test matrices return a 0^0 Indeterminate error .
m={{1,-\[Sqrt]3,0},{\[Sqrt]3,-1,0},{0,0,1}};
m^0
I am just wondering what's going on here.
Where I encountered this funny behavior:
I want to check if the infinite power series of a matrix returns the MatrixExp[]. The series starts with the 0th power.
[1]: https://mathworld.wolfram.com/MatrixPower.htmlRaspi Rascal2020-12-05T02:31:03ZJosephus Problem: queue data structure as circular list
https://community.wolfram.com/groups/-/m/t/2127925
&[Wolfram Notebook][1]
[Original]: https://www.wolframcloud.com/obj/shenghuiy/Published/josephProblem2.nb
[1]: https://www.wolframcloud.com/obj/wolfram-community/Published/josephProblem3.nbShenghui Yang2020-12-01T20:42:05ZReducing 3rd-order linear ODEs to v''' + Z v = F with a change of variables
https://community.wolfram.com/groups/-/m/t/2125432
&[Wolfram Notebook][1]
[Original]: https://www.wolframcloud.com/obj/rauan234/Published/Simplifying%203rd%20order%20ODE.nb
[1]: https://www.wolframcloud.com/obj/wolfram-community/Published/Simplifying_3rd_order_ODE%282%29.nbRauan Kaldybaev2020-11-29T08:22:03ZSolve a system of ODE's with DSolve[ ]?
https://community.wolfram.com/groups/-/m/t/2126282
I'm new to Mathematica and would appreciate anyone with an experienced eye who would look at the following failed attempt to solve a system of ordinary differential equations and tell me what I'm doing wrong. The function is pasted below and a .nb file is attached.
I'm looking for general symbolic solution to a standard S,I,R (susceptible, infected, recovered) model. Then I'd like to learn how to play with parameters and plotting features. But first, I need a solution. This attached formulation has been running for a few hours without returning a result. What's wrong with its arguments? Is there a way to limit parameter intervals and independent variable interval?
Thanks.
eqns = {s'[t] == m (s0 + i0 + r0) - \[Beta] s[t] i[t] - m s[t], i'[t] == \[Beta] s[t] i[t] - m i[t] - g i[t], r'[t] == g i[t] - m r[t]}
sol = DSolve[eqns, {s, i, r}, t]Jay Gourley2020-11-30T23:02:37ZIsolate imaginary/real part of simple algebraic expression?
https://community.wolfram.com/groups/-/m/t/2125252
Using Mathematica can be often very frustrating. Either I'm doing something wrong here, or Mathematica is just dumb.
So, I have the below expression:
-1 + ((2*I*(1 + Log[Pi] - (I*Pi)/2))/Pi)*(r + I*t)
And I am trying to put it in form a+i*b, nothing complicated at all, but Mathematica chokes on it.
I tried to use the below, but it's ignoring my attempts to tell it that r and t are reals:
In[298]:= Clear[r, t]; x1 = -1 + ((2*I*(1 + Log[Pi] - (I*Pi)/2))/
Pi)*(r + I*t);
FullSimplify[Abs[x1]*Cos[Arg[x1]], Assumptions ->
r*In*Reals && t*In*Reals]
Out[298]= -1 - Im[t] + Re[r] - (2*(1 + Log[Pi])*(Im[r] + Re[t]))/Pi
Where am I going wrong? Please help, I really appreciate.Jose Sousa2020-11-28T05:43:21ZHow to clear the previous input
https://community.wolfram.com/groups/-/m/t/2127361
I input a function y’[x] in input 26
When i want to solve a differential equation,
I entered
y’’[x]-3y’[x]+2y=0 in input 27. However, the system shows invalid argument as it considered the input 26 as the y’[x] in input 27
How can i do so?
Please help me with that.Cheuk Hin Ng2020-12-01T17:07:41ZLinear secret-sharing: generalizing Shamir's scheme
https://community.wolfram.com/groups/-/m/t/2121685
&[Wolfram Notebook][1]
[Original]: https://www.wolframcloud.com/obj/jose.manuel.rodriguez.caballero/Published/SecretSharingGF.nb
[1]: https://www.wolframcloud.com/obj/wolfram-community/Published/SecretSharingGF3.nbJosé Manuel Rodríguez Caballero2020-11-24T01:44:39ZDifferent periodicity for equivalent equations in W|A?
https://community.wolfram.com/groups/-/m/t/2127261
Hello,
I was investigating the equation `sin(sin(x))/sin(2sin(x))` in my work. When I type it on Wolfram|Alpha, it says the periodicity is 2π and the result is 'csc(2 sin(x)) sin(sin(x))', whose periodicity is also 2π.
However, Wolfram|Alpha also says such equations are equivalent to '1/(2*cos(sin(x)))' (also represented as 'sec(sin(x))/2)'). When I type these equations on Wolfram|Alpha, it says the periodicity is only π.
It's very strange. When I type 'csc(2 sin(x)) sin(sin(x)) - sec(sin(x))/2)', the result is 0 (indicating they are the same equation), but they present different periodicity according to the same website.Marlon Saveri2020-12-01T12:18:30ZAdd a line (y=a*x+b) to a ListPlot graph?
https://community.wolfram.com/groups/-/m/t/2125276
I am studying the Riemann zeta function, and I've created this cool graph which for a given Re(s) in the critical strip, it generates a graph of values given by a certain function, *y=f(x)*.
When the graph crosses a certain line (*y=2 x*), that point represents a zero of the zeta function.
Anyway, I'm not gonna give many details because this is a preliminary paper, a work in progress, and I don't want to say things that are not proven yet.
But anyway, how do I add a line (*y=2 x*) to this plot? Thanks so much.
Here's my code (**redacted**):
$MaxExtraPrecision = 500; Clear[t]; r = 3/4; x0 = -3/2; m = 3; l =
Round[x0 + m, 1]; k = 80;
f[t_] :=redacted; s =
Table[{n = x0 + m (q - 1)/(k - 1), f[n]}, {q, 1, k}]; g2 =
ListPlot[s, Joined -> True, ImageSize -> Large,
PlotStyle -> {Thickness[Tiny]},
GridLines -> {Table[i, {i, -l, l}], Table[f[i], {i, -l, l}]}]
Please let me know where in this code I need to add the line, and more importantly **how**.
Thanks so much!
![enter image description here][1]
[1]: https://community.wolfram.com//c/portal/getImageAttachment?filename=Graph.PNG&userId=1643856Jose Sousa2020-11-28T09:06:28Z