This tag is intended for the review and improvement of style for already functioning code. It not meant to change the objective of the code.

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0answers
71 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 ...
17
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1answer
241 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
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0answers
165 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
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1answer
101 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
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1answer
30 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
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1answer
50 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
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1answer
35 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
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0answers
78 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 ...
26
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1answer
854 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 ...
1
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2answers
91 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
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1answer
59 views

usage of random numbers in recursive loop

I am trying to evalute two functions using iterative process as below ...
2
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2answers
68 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
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0answers
66 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
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1answer
38 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 ...
25
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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
189 views

How to make multiple if statements?

I know Mathematica's if format is If[test, then result, else alternative] For example, this ...
1
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1answer
66 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
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3answers
378 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
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0answers
58 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 ...
21
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2answers
472 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
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7answers
765 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
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1answer
56 views
0
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0answers
47 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
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0answers
87 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
130 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: ...
2
votes
2answers
79 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
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1answer
52 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
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1answer
349 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
173 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
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1answer
55 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
49 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
103 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. ...
4
votes
2answers
394 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 ...
1
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1answer
103 views
4
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2answers
189 views

Generate lists that satisfy a condition in an efficient way

The following code produces lists of sublists with maximum length 5 that shuffle zeros around an ordered list (here {1,2}). It produces all permutations while ...
1
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1answer
245 views

Lookup construction using data matrix and Reap/Sow versus AppendTo`s

I am a user of MMA9 and made my own kind of Lookup, which is now a standard command in Version 10. In my program there is a section in which by means of a StringReplace[ ]-command containing a lot of ...
1
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0answers
74 views

Am I simulating correctly my hidden markov chain?

I want to simulate a hidden markov model, in which $y_t|y_{t-1},x_t=i \sim N(\theta_0y_{t-1}+\theta_i,\sigma^2)$, where $y_t$ is the observations or data, and $x_t$ is the state variable of the ...
1
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0answers
57 views

Problem with converting recursive code to iterative

I am trying to convert a snippet that uses recursion into one that uses iteration for drawing an L-tree, but my code produces duplicate points. How do I avoid generating them? Recursive version: ...
1
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1answer
101 views

Plot multiple solutions [duplicate]

I want to plot multiple solutions of an equation, so that one can differ them in the plot. The given equation is e.g. ...
2
votes
0answers
69 views
0
votes
1answer
162 views

Optimizing Chi-square distance between two distribution

I want to program the chi-square between two distribution Xu and Vu with length N. This function is defined as below: Xu and Vu are real and positive. ...
1
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0answers
53 views

Implementing normalization/rescalement from a Tutorial

I'm trying to implement a rescale/normalization as is described in here by mathematical expressions in page 10, and code in the top part of page 16. The notebook is also available here. The objective ...
1
vote
1answer
106 views

C compiler error: the no library could be generated error

I have windows 8, Mathematica 9, and I've just installed Microsoft Visual Studio 2013 with update 3. I'm try to run Compile with the option ...
3
votes
1answer
128 views
2
votes
0answers
52 views

Number recognition in Mathematica [closed]

Suppose that I have a number $n$ with many decimal digits of precision. What is the code to use to get Mathematica to recognize possible closed-form expressions for that number?
0
votes
1answer
89 views

How to compute an integral with 300 digits accuracy [closed]

I'm new to Mathematica and I would like to ask what is the code to use to calculate numerically an integral with 300 digits precision; also, I would like to know what is the right code to use the ...