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3
votes
2answers
68 views

How to define UpValues about the derivative of NBSpline when the length of knots is unknown?

Description In the book “Programming in Mathematica” 3rd by Roman.E.Maeder, the author gives a topic about A new Mathematical Function in section 8.4. For instance, for the following formula: ...
1
vote
0answers
38 views

Reducing quantile & color map queries for use with Associations

This set of queries perform basic maps to quantile and then color-map. There's got to be a more compact solution. What are some approaches to reduction? Numeric: ...
3
votes
0answers
58 views

Memory Management for Large Datasets [on hold]

I've written some Mathematica code to generate polynomial roots. The code take an argument n as the highest degree of polynomial to solve for and then exports a file containing a list of the roots: ...
2
votes
1answer
233 views

Runge-Kutta-2 on System

After spending some time using the Mathematica documentation and this Mathematica.SE answer, I implemented the Runge-Kutta-2 routines. I am hoping someone can validate what I did and tell me that it ...
1
vote
1answer
42 views

Sort and Save Matrices Eigenvectors to a Larger Matrix

We are going to sort and save all orthoginalized-eigenvectors of 4*4 random matrices (produced in any iteration) to a larger matrix such as storagematrix. Since, produced random matrices are 4*4, ...
30
votes
1answer
1k views

May the Fourth be with you

Happy Star Wars day. I was playing around with the image manipulation functions in Mathematica in an attempt to recreate the Star Wars crawl. There's an HTML/CSS implementation which is in my ...
5
votes
1answer
106 views

Composition vs serial assignment, which performs better?

I have a giant block of code that manipulations an expression in many different ways. Currently it looks like ...
1
vote
2answers
158 views

Having trouble translating Matlab `fsolve` into Mathematica

I searched the site and found that someone said FindRoot is equivalent to fsolve, however, without proper options, ...
28
votes
1answer
932 views

Fast Spherical Harmonics radiative transfer

This is a rather specific question and I apologize for spamming you with some lengthy code. But it could be interesting for some reader and maybe you can help out, so please bear with me. I am using ...
3
votes
2answers
143 views
0
votes
0answers
60 views

Inverse Superposition

There are 4 tables that, I have written them as bellow: (m, n, s, and r are orthogonal basis. r.r=n.n=m.m=s.s=1, and m.n=n.r=...=0). a's, b's, c's and d's are coefficients and are numeric values. ...
-1
votes
1answer
212 views

Some Problem with WhenEvent! [closed]

Anyone knows what's the problem with the following code and how can I fix it? I am not sure that I wrote the WhenEvent section correctly. By the way, I want to solve the equations and then plot y vs. ...
14
votes
4answers
609 views

Button evaluation inside DynamicModule

Someone know why this Button works when clicked: ...
5
votes
0answers
82 views

Forecasting problem with Geometric Brownian Motion in Wolfram Mathematica [closed]

I'm a full time undergraduate student from Peru, and I'm trying to use the Geometric Brownian Motion example used in the help section from Wolfram Mathematica in order to forecast future stock ...
6
votes
0answers
111 views

Fine tuning compiled code that computes dilogarithm function

As an exercise of writing a good Compile function, I want to do the simple task of coding a routine that outputs the real part of the dilogarithm function ...
1
vote
0answers
98 views

How can I improve the solution of my PDE?

I want to improve the last code to find a better solution for umi. For now I'm using only MaxStepFraction. Also, when I put no ...
19
votes
1answer
270 views

Segmentation of sunspots

I recently went for a walk with my camera and snapped a few pictures of the sun. The pictures didn't turn out too well, but this was to be expected without a telescope. I thought it might be a nice ...
3
votes
0answers
181 views

Nonlinear FEM and FindRoot

I'm trying to develop a kind of nonlinear FEM application using mathematica to solve a bvp like the following: $$ \gamma(u') ~u^{iv} + 2 \gamma'(u') u''' u''+ u''^3 = f(x) $$ where $u = ...
1
vote
1answer
112 views

Hill function (equation) vs a gene

So im trying to make one equation equal another to solve for all physically realistic values of $X$. Hill function is: $$ F(X)=\frac{1}{1+(\frac{X}{K})^n} $$ and Gene Z equation is: $$ Z(X) = ...
0
votes
1answer
33 views

Error message with Animate?

I have a error message, but after I execute ndsolve cell is all right.What is the Reason for this error? ...
2
votes
1answer
56 views

Plot directional field with a initial vlue

I do not have enough reputation to comment on other questions, hence I have to ask my own one I want to solve the following nonlinear first order ODE, $$(1 + x) (0.5 y[x]^{-0.5} (x - y[x])^{0.5} - ...
0
votes
1answer
39 views

How to get the dynamic expression

$$Z_{n+1}=\frac{\alpha Z_n}{1+Z_{n-1}}$$ How to write the above expression in Mathematica? I want to get say Z_100, Z_10 by that scheme. Can I call say $Z_{10}$ if $Z_{n+1}$ is given?
5
votes
0answers
87 views

How can I do a two dimensional `Fold`?

I'd like to Fold over higher dimensional objects than lists. Semantically, the format would be something like ...
1
vote
2answers
96 views

How to find total distance covered when I have a list of GeoPositions?

So I have a list of GeoPositions and I need to find the distance covered in that order? I know I can find the distance from each city and then add them all up but I was wondering if there is any ...
0
votes
1answer
67 views

usage of random numbers in recursive loop

I am trying to evalute two functions using iterative process as below ...
2
votes
2answers
73 views

Arrangements (?) from permutations of rows in a triangle, is there a simpler way to program this?

I am generally confused about integer valued polynomials, and how to count them. Trying to learn the subject I started by listing permutations of the rows in a lower triangular table: $$\displaystyle ...
0
votes
0answers
67 views

Matrix iteration failing after second step

I am calculating 11x6 matrix using different logics as in below code. Problem is in Do loop in below code where I have two different criteria to update matrix "fd". I am expecting logic in IF which ...
0
votes
1answer
48 views

Sampling Points Between Two Functions and Plotting Sample Points? (I have partial code) [duplicate]

I want to sample random points between $Cos(x)$ and $Sin(x)$ on $0 \le x\le \frac \pi4$ I was able to do graph the function here in Mathematica. I would like to count, and then plot points between ...
26
votes
7answers
1k views

Splitting words into specific fragments

I am looking into splitting words into a succession of chemical elements symbols, where possible. For example: Titanic = Ti Ta Ni C (titanium, tantalum, nickel, carbon) A word may or may not be ...
2
votes
4answers
204 views

How to make multiple if statements?

I know Mathematica's if format is If[test, then result, else alternative] For example, this ...
1
vote
1answer
68 views

How would I go about simulating conditional random birth 100 times?

So I have the following scenario: Assume you have this organism that reproduces by itself. An organism either reproduces 0, 1, 2, or 3 organisms at a time. Assume they're asexual and reproduce only ...
1
vote
3answers
393 views

How to simplify and shorten pattern code?

I this code to sorting only those tuples that are have total sum of 15 without repetition.: ...
0
votes
0answers
62 views

Optimising prime number test code

Is it possible to speed-up this code ? Also, It would be great if people could test this algorithm. I only have a Raspberry Pi to test it on, so I can't be certain it's not a strong probable prime ...
22
votes
2answers
495 views

Copying one symbol into another

I would like to know how can I completely copy one Symbol to another. When I say copy, a refer to UpValues, DownValues, ...
13
votes
7answers
780 views

How to sort digits in a string while keeping other characters untouched?

Now there is a string with digits and letters, for instance, "95uge678r3gi89hgfe30kgh063d51". And the expected output is ...
0
votes
1answer
62 views
0
votes
0answers
55 views

How to eliminate all terms of a variable with square root in an equation?

I did the following thing: take an equation with square root terms, by moving terms and squaring two sides, finally ending up with a polynomial of the specific variable. My algorithm is like this: ...
1
vote
0answers
101 views

Collision detection algorithm (discrete) with sweep and prune algorithm for periodic boundary conditions

EDIT: Question Updated with solution approach, but solution much slower than original implementation. Any ideas to speed up implementation? In the discussion on collision detection (see here) I asked ...
3
votes
1answer
137 views

How to accelerate my code?

Given a 2D $M \times N$ matrix with non-negative values, I would like to find a path going from top to bottom such that the sum of the path is minimum. My function is defined as follow: ...
3
votes
2answers
104 views

Finding large Collatz Sequences, trying to improve speed

Background: I am already very much in love with Mathematica but I am also a novice. So far I have only gathered experience in procedural programming in Python. Generally speaking I am trying to ...
0
votes
1answer
61 views

Solving coupled ODEs with NDSolve

Given the system of differential equations: $i\frac{d}{dt}c_{1}(t)=H_{12} E(t)e^{(iw_{12}t)}c_2(t)+H_{13} E(t)e^{(iw_{13}t)}c_3(t)$, $i\frac{d}{dt}c_{2}(t)=H_{21} E(t)e^{(iw_{21}t)}c_2(t)+H_{13} ...
10
votes
1answer
365 views

How to visualize pattern matching process?

I want a function that does the same job like ReplaceRepeated, and can make the matching process visible. I searched the Internet but didn't find any existing code ...
6
votes
2answers
191 views

Efficient Lloyd Sampling of Images

I want to sample a grayscale image so that every voronoi cell contains approximately the same total intensity using lloyd sampling. My current code is kind of slow and I was hoping for some advice to ...
1
vote
1answer
58 views

Is this caused by meomory usage ? (Something odd/hard to describe)

I really can't make a "smaller" example, but the files are here, for the data and for the notebook. It will cost a LOT of memory, up to 30G of RAM (maybe more). Here is the problem, (from a Linux ...
3
votes
3answers
1k views

Using DSolve to solve for x[t,parameter]

I'm trying to solve an ODE with two independent variables (a cannon firing from a cliff incorporating wind resistance dependent on velocity). I've tried the following for the x-component: ...
0
votes
0answers
50 views

How to Fold (FoldList) this in a more compact (efficient) way?

Example code: x = Table[something[i], {i, 5}] Table[Fold[f1[#1, f2[#2, a], a] &, x[[i]], {c1, c2, c3}], {i, Length[x]}] This above is just an example. I ...
1
vote
1answer
121 views

How to rewrite a nested loop with Reap and Sow [closed]

I was wondering if anyone know how to rewrite the following nested loop but using Reap and Sow. I need to reduce the execution time. Thank you. ...
5
votes
2answers
404 views

Code elegance and compactness. Help needed with Map, Apply

I need some help with code optimization and compactness. I have a set of two-dimensional points and I can use the Mathematica function FindClusters to find 4 clusters. I'd like to plot the points ...