/r/Mathematica

Photograph via snooOG

For information and tips about Mathematica features.


related reddits:

/r/Mathematica

10,506 Subscribers

0

why self loops

Why am I getting self loops with this simple code when the main diagonal is all zeros?

ku = {{0, 40, 0}, {1, 0, 1}, {0, 15, 0}}

WeightedAdjacencyGraph[ku, EdgeLabels -> "EdgeWeight"]

3 Comments
2024/06/26
20:02 UTC

3

WignerD orthogonality relation

Hi guys.

Can someone help me undestand why the WignerD function is not satisfying the orthogonality relation for (j,m1,m2) = (1/2, 1/2, 1/2) and (j', m1', m2') = (1, 0, 0)?

https://preview.redd.it/yot38uu0ez7d1.png?width=733&format=png&auto=webp&s=21d0b77f77f35073c191804476e6091cd5820a65

https://preview.redd.it/kyu3y3b2ez7d1.png?width=828&format=png&auto=webp&s=883ed74f844bdd4e26681107772ec2b234d3ab6e

7 Comments
2024/06/21
20:03 UTC

1

Is 28% off a good discount for the Home Premium Plus plan?

Is 28% off a good discount for the Home Premium Plus plan? Looking to get a good discount can wait for black friday or whatever.

0 Comments
2024/06/21
13:51 UTC

1

why $MachinePrecision can have a value of 15.9546?

But at the same time, InputForm[3.1^10] gets me 81962.82869808013, a 16 digit machine number. So doesn't this show that $MachinePrecision should be 16 instead?

4 Comments
2024/06/19
17:03 UTC

0

AI Copilot in your Notebook. Part 2 🤖

0 Comments
2024/06/17
11:55 UTC

0

Please help me

Explain the meaning of linear Programming? what is a linear Programming problem? Give the formulation of the general linear Programming problem? Explain with an example? Define feasible region, Objective function, Decision variables?

9 Comments
2024/06/15
08:07 UTC

5

We made AI copilot for computational notebook using GPT4o 🤖

https://youtube.com/shorts/wenBdDRpD4g?si=yO4OZHk6XnfjBwJj

We deeply integrate an AI assistant to our notebook interface. It is free. It can evaluate, edit, comment on cells and write in multiple languages.

The general idea is to utilize OpenAI API functions, we implemented the following functions:

  1. Get notebook structure (as json)
  2. Get cell’s attributes (by uid)
  3. Get cell’s content
  4. Set cell’s content
  5. Get current cell (as uid)
  6. Make a request to Wolfram Alpha (knowledge base)
  7. Create new cell after or before the given one by uid
  8. Delete cell by uid

Combining it with ~3000 tokens initial system prompt giving the details of the notebook environment, used languages and libraries it works quite well as a sort of copilot.

Our project is open-source and free.

See more WLJS Notebook Github: https://github.com/JerryI/wolfram-js-frontend Docs: https://jerryi.github.io/wljs-docs/

7 Comments
2024/06/14
05:30 UTC

1

How to make graph with multiple animations with one variable

i am trying to create simple solar system simulation mine code for planets looks like this :

w7 = PolarPlot[puran/(

1 + \[Epsilon]uran*Cos[t + urak]), {t, 0, 2 \[Pi]},

Epilog -> {Green, PointSize[Large],

Point[{auran (1 - \[Epsilon]uran*

Cos[ResourceFunction["KeplerE"][\[Epsilon]uran, (2 \[Pi])/

Puran*(czas - tpuran)]])*

Cos[2*ArcTan[

Sqrt[(1 + \[Epsilon]uran)/(1 - \[Epsilon]uran)]*

Tan[ResourceFunction["KeplerE"][\[Epsilon]uran, (

2 \[Pi])/Puran*(czas - tpuran)]/2]] - urak],

auran (1 - \[Epsilon]uran*

Cos[ResourceFunction["KeplerE"][\[Epsilon]uran, (2 \[Pi])/

Puran*(czas - tpuran)]])*

Sin[2*ArcTan[

Sqrt[(1 + \[Epsilon]uran)/(1 - \[Epsilon]uran)]*

Tan[ResourceFunction["KeplerE"][\[Epsilon]uran, (

2 \[Pi])/Puran*(czas - tpuran)]/2]] - urak]}]}];

Where Polarplot creates an orbit outlier and rest is responsible for planet the variable connecting every plot is (czas) also when i use Animate function for one code everything works i just need to combine them in comments ill add picture of one plot. other variables are predetermined number or are correlated with current time to determine actual position.

https://preview.redd.it/n7l2aekgbz5d1.png?width=1319&format=png&auto=webp&s=66af8962b367d45a78d1b272d7685a67aec11c8f

3 Comments
2024/06/11
17:34 UTC

2

NullSpace of row vector

Hello,

how can I calculate the NullSpace of a row vector e.g (4, 2, 6) in mathematica.

A basis of the NullSpace would be a*(1/2, -1, 0) + b*(3/2, 0, -1).

When I try NullSpace[{4,2,6}] or Transpose[{4,2,6}] it doesn't work and it says

"Argument {4,2,6} at position 1 is not a non-empty rectangular matrix"

2 Comments
2024/06/09
19:10 UTC

2

Can Mathematica solve an optimization problem with parameters?

Very new to Mathematica so I apologize if this is a stupid question.

I am trying to maximize the following function:

(e - s)^\alpha - \frac{e^\beta}{s}

Where:

0 <= e <= 1 AND 0 <= s <= e

Obviously the maximum value will depend on the parameters \alpha and \beta and that is exactly what I want i.e. I want a function of \alpha and \beta.

Is there a way to compute this is Mathematica? I have so far tried using the Maximize function but keep getting errors or non-sensical answers. Would appreciate any help.

Edit: I am using the following code:

Maximize[{(e - s)^(a) - (e^(b))/s, 0. <= e <= 1 && 0. <= s <= e}, {e, s}]

The output just returns the command.

3 Comments
2024/06/06
20:48 UTC

2

How to change magnification of toolbar and suggestion bar?

I just changed from Mathematica 12 to 14 and everything is so much larger. When I change the magnification from 100% to 75%, it only reduces the size of the text inside the input and output cells. The icons of the toolbar and text (and bar size) of the suggestion bar remains unaffected.

At 100% Magnification

At 75% Magnification

I have also found this to be peculiar, since my monitors are both 1920x1080 monitors (I have two).

https://preview.redd.it/vx5cwkm4hp4d1.png?width=727&format=png&auto=webp&s=1a9f8249ec2d98fb1b4ebbf8973cf61bc2f92b35

Is there is anyway to make the everything (toolbar icons, suggestion bar font, suggestion bar size) smaller?

1 Comment
2024/06/05
07:32 UTC

2

I have been facing this problem with this problem: "Solve: This system cannot be solved with the methods available to Solve"

This the thing that i'm trying to calculate.

Ne = ConditionalExpression[-((

2 f^2 (-Log[Sin[phik/(2 f)]] +

Log[Sin[1/

2 (ArcCos[-(f^2/(f^2 + mpl^2))] +

2 \[Pi] ConditionalExpression[1, \[Placeholder]])]]))/

mpl^2), And[

Element[

C[1], Integers], Cos[Rational[1, 2] f^(-1) phif] >= 0,

Cos[Rational[1, 2] f^(-1) phik] >= 0,

Tan[Rational[1, 2] f^(-1) phif] >= 0,

Tan[Rational[1, 2] f^(-1) phik] >= 0]];

Solve[Ne == 50, phik]

3 Comments
2024/06/05
01:05 UTC

2

Help with FindRoot

I have a 3 component parametric function with randomly generated parameters:

function = {Sqrt[(0. + 0.0878006 t - 0.996037 Sin[2.97945 t])^2 + (0. + 
    0.31493 t + 0.0142161 Sin[2.97945 t])^2], 
 ArcTan[0. + 0.0878006 t - 0.996037 Sin[2.97945 t], 
  0. + 0.31493 t + 0.0142161 Sin[2.97945 t]], 
 0. - 0.945045 t - 0.0878006 Sin[2.97945 t]}

I want to find where the first component is equal to any of the values from the following list:
List = {3.10, 5.05, 8.85, 12.25}~Join~{29.9, 37.1, 44.3, 51.4}

I know that there could be multiple solutions for t for each value in the list, so to find all the solutions I make a table of tables of solutions with FindRoot (with the intention of deleting duplicate solutions later), where I increment both the starting guess for t = t0, and the value from List.

NumTimesteps = 15
timeStep = 1
IntersectionTimes = 
  Table[Table[FindRoot[function[[1]] - List[[i]], {t, timeStep j, 0, Infinity}], {i, 1,Length[list]}], {j, 0, NumTimesteps}];
IntersectionPoints = Table[function /. IntersectionTimes[[i]], {i, 1, 
    Length[IntersectionTimes]}]; 
UniqueIntersectionPoints = DeleteDuplicates[SetPrecision[IntersectionPoints, 5]] // MatrixForm

This code finds a list of t values using FindRoot that satisfies:

 function[[1]] - List[[i]] ==0

Output of the FindRoot Table

And to the best of my knowledge, if we plug those t values back into our function, then the first component of every 3 component vector function(t) should give a value in the List. However this is not the case. MOST of the first components are in the list, but notice in the output there is a first component of function(t) of 2.7361, which is NOT in the list. Further, the last line does not seem to delete duplicates. Anyone know what is going on here??

4 Comments
2024/06/03
18:20 UTC

1

Help with FindInstance

I have this:

v = {1, 2, 5, 3};
var = {1, 2, x3, x4};
FindInstance[Intersection[var, v] == v, {x3, x4}, Integers]

Im expecting having this result:

solutions = {
{x3 -> 3, x4 -> 5},
{x3 -> 5, x4 -> 3}
}

However is giving me {}

What im doing wrong?. How i can fix it?

2 Comments
2024/06/03
09:44 UTC

1

Can I use Mathematica to calculate step by step solutions? If so, how?

as per title, thanks!

9 Comments
2024/06/02
18:15 UTC

12

Bad Apple, but its Wolfram Plot

This is a realtime animation made in WLJS Notebook with a simple FindShortestTour function.

Check the full story on medium if you are interested in implementation

1 Comment
2024/06/02
11:30 UTC

3

Two seeming errors in Mathematica, does anyone know more?

In[101]:= Limit[Gamma[x]/x^33, x -> Infinity]                                   

Out[101]= Infinity

In[102]:= Limit[Gamma[x]/x^34, x -> Infinity]                                   

Out[102]= 0

In reality, I believe Gamma[x]/x^n for any large n has a limit of Infinity eventually

In[103]:= IntegerQ[Log[64]/Log[2]]                                              

Out[103]= False

In[104]:= IntegerQ[Simplify[Log[64]/Log[2]]]                                    

Out[104]= False

but 6 IS an integer

6 Comments
2024/05/29
14:36 UTC

1

Generating proofs for arithmetic problems

Folks, what are some ways/approaches to create mathematical proofs. How could one use Mathematicas built in tools which integrate with OpenAI ChatGPT to solve the problem described ?

https://www.reddit.com/r/mathematics/comments/1d1coqg/human_ai_combo_to_solve_arithmetic_problems_can/

2 Comments
2024/05/26
22:34 UTC

1

How to modelize a crochet pattern ?

For a presentation I chose to try to present the link between crochet and maths and I wanted to create a mathematical serie for a simple sphere pattern but I can’t figure it out. If anyone could help me it would be with great pleasure !

0 Comments
2024/05/21
19:21 UTC

5

Worth learning Mathematica over the summer for a freshman Applied Math major?

My daughter just graduated HS and will be majoring in applied math this fall. I use Mathematica once in a while as an EE and have it at work, but not heavily.

Is it worth me getting her the student version so she can take one of the online intro classes over the summer? Or should she just stick with pencil and paper? I figure it would be usefull for plotting, etc. she does know basic Python.

14 Comments
2024/05/21
16:37 UTC

1

Replacement rules for non-commuting objects

I'm trying to tell Mathematica to make some replacements and I'm running into some problems.

The first one is the following:

1/f A.B.C /. B->(f D)

gives me

1/f A.(f D).C .

How do I tell Mathematica that f is a scalar?

The second one is probably related:

A.D.C f /. D f->C

doesn't change anything. I gues it's also because Mathematica doesn't know that f is a scalar. So again, how do I tell Mathemafica that f is a scalar?

1 Comment
2024/05/21
13:31 UTC


1

NDSolve Help: "0.0127 is not a valid variable"

Hi all, I'm struggling to understand why Mathematica spits out "0.0127 is not a valid variable." I assume it has something to do with the format of the BC's, but I couldn't figure out a solution. Here is my code:

(*Define parameters*)\[Rho]=8914.309767; (*Density*)
Cp=385.5928; (*Specific heat capacity*)
k=395; (*Thermal conductivity*)
R=0.0127; (*Radius of the cylinder*)
g=9.80665; (*Gravitational acceleration*)
T\[Infinity]=328.15; (*Ambient temperature*)
T0=295.9166667; (*Initial temperature at t=0*)
tmax=200; (*Maximum time for the simulation*)
\[Epsilon]=10^-6; (*Small positive value to approximate r->0*)

(*Solve the PDE using NDSolve*)
solution=NDSolve[{\[Rho] Cp D[T[t,r],t]==k (D[T[t,r],{r,2}]+(1/r) D[T[t,r],r]),T[0,r]==T0,(T^(0,1))[t,\[Epsilon]]==0,(T^(0,1))[t,R]+0.48 (g/(2*R))^(1/4)*((-0.0039142857 ((T\[Infinity]-T[t,R])/2)^2-0.0655238095 ((T\[Infinity]-T[t,R])/2)+1001.1128571429)*(-0.000000051428571 ((T\[Infinity]-T[t,R])/2)^2+0.000011954285714 ((T\[Infinity]-T[t,R])/2)-0.0000108)/(0.000000203583385 ((T\[Infinity]-T[t,R])/2)^2-0.000029440675203 ((T\[Infinity]-T[t,R])/2)+0.001503110306059)/(-2.31713716*10^-12 ((T\[Infinity]-T[t,R])/2)^2+5.5756112918*10^-10 ((T\[Infinity]-T[t,R])/2)+1.3315500052471*10^-7)*(T\[Infinity]-T[t,R]))^(1/4)*(T[t,R]-T\[Infinity])==0},T,{t,0,tmax},{r,\[Epsilon],R}];

(*Extract the temperature at the center of the cylinder (r->0)*)
temperatureAtCenter=T[t,\[Epsilon]]/. solution;

(*Plot the temperature at the center of the cylinder as a function of time*)
Plot[Evaluate[temperatureAtCenter],{t,0,tmax},PlotLabel->"Temperature at Cylinder Center (r -> 0) vs Time",AxesLabel->{"Time (s)","Temperature (K)"},PlotRange->All]
5 Comments
2024/05/18
02:52 UTC

1

What is the big difference between downloading Mathematica for Sites instead of Mathematica for Students (for Sites)?

Basically all my question is the one in the title, I got licenses for the version 14.0.0 of both products but I don’t know which is their difference.

5 Comments
2024/05/16
17:18 UTC

7

I obviously don't understand Mathematica

I find myself constantly quitting the kernel and running the notebook from scratch. I don't want whatever cached artifacts there are from previous runs causing errors.

Compare Matlab, where I just run the script again and whatever values I set overwrite the values that exist. Why doesn't Mathematica work this way?

Quitting the kernel all the time can't possibly be the proper workflow.

What am I missing?

7 Comments
2024/05/16
01:47 UTC

Back To Top