## Top new questions this week:

### Values of counting functions

I have a table of integers, say A, and consider the counting function C, which, for a given x, gives the number of elements in A which are less or equal to x. Next, I want to plot C(x) in some range, ...

list-manipulation performance-tuning counting
 asked by Maciej Ulas Score of 7
 answered by Henrik Schumacher Score of 7

### Apply pattern using a Slot (#) to each list element using a second slot

I am trying to find a neat way of applying an operation to each list element, but do not know how to properly use multiple slots or whether it is actually possible to solve this with multiple slots. I ...

list-manipulation pattern-matching filtering associations slot
 asked by michelangelov Score of 6
 answered by E. Chan-López Score of 4

### Sorting a list by a single particular element in a specified order

I have a list of lists -- a list of sublists -- that I wish to sort in a specified order. The following function, sortBy2ndElement, sorts a list of lists (...

sorting
 asked by Andrew Score of 5
 answered by kglr Score of 8

### Inaccuracy for FEM for 3D Heat Equation

I'm simulating the heat transfer within a cylindrical rod, with external heating from its sides. ...

finite-element-method heat-equation
 asked by Lucas Score of 5
 answered by Ulrich Neumann Score of 3

### Mesh Cylinder[{{0,0,0},{0,0,1}},1] with inner boundary x=y=0

In a meshed cylinder Cylinder[{{0,0,0},{0,0,1}},1] I need to specify DirichletConditions along ...

finite-element-method mesh
 asked by Ulrich Neumann Score of 5
 answered by andre314 Score of 6

### Minimizing computational time for a quantum walk problem

Any suggestions as to how to speed up the computational time for this quantum walk problem which is coded using a normalized SparseArray coin operator as follows: ...

matrix performance-tuning sparse-arrays quantum-computing
 asked by thils Score of 5
 answered by thils Score of 3

### How to remove double ticks in bar charts and remove/ extend space between bars?

This is the bar chart. I need to remove the overextensions of the bar lines, reduce the space between consecutive A,B,C,D. However, I also want to retain/ add space between the three groups of ...

plotting output-formatting charts
 asked by krygh Score of 4

## Greatest hits from previous weeks:

### Finding unit tangent, normal, and binormal vectors for a given r(t)

For my Calc III class, I need to find $T(t), N(t)$, and $B(t)$ for $t=1, 2$, and $-1$, given $r(t)=\{t,t^2,t^3\}$. I've got Mathematica, but I've never used it before and I'm not sure how to coerce ...

equation-solving calculus-and-analysis geometry vector-calculus homework
 asked by a98 Score of 32
 answered by Artes Score of 47

### Conversion of Sine to Cosine

I'm solving equations with many Cosines and Sines. And I want to convert all the Sines to Cosines using trigonometric formulas such as cos(x)=sin(x+pi/2). How can I do this?

trigonometry conversion
 asked by YongCheol Kwon Score of 5
 answered by Sjoerd C. de Vries Score of 2

### Is there an open source implementation of Mathematica-the-language?

I've seen questions before such as "What is the best open-source equivalent for Mathematica?", but that specific question (and that line of inquiry in general) cares more about the computer algebra ...

programming open-source
 asked by sblom Score of 129
 answered by Simon Score of 92

### Drawing a square root spiral

Here is a start. I'm looking for a nice way to draw it. ...

graphics geometry
 asked by matrix42 Score of 24
 answered by Bob Hanlon Score of 23

### $\LaTeX$ and Mathematica

I quite often would like to draw graphics in my $\LaTeX$ documents using Mathematica. I have encountered three problems. I would like to know if there are any workarounds to these problems I would ...

graphics export latex
 asked by Thomas Rot Score of 137
 answered by Simon Score of 47

### How to make the digits of π go around in a spiral like this?

Here is a start. MapIndexed[Text[Reverse[First[RealDigits[Pi,10,252]]][[Tr@#2]],#]&, Table[{t Cos[t],t Sin[t]},{t,0,16Pi,0.2}]]//Graphics

graphics formatting generative-art
 asked by matrix42 Score of 58
 answered by Martin Ender Score of 74

### Mathematica code for Bifurcation Diagram

At the moment I am trying to construct a bifurcation diagram of the iterative function $f(x)=$ $ax-1.1975x^3$. I've scoured the internet for pre-made bifurcation diagrams and found many (mostly of the ...

plotting graphics code-request
 asked by Mel Score of 31
 answered by Mark McClure Score of 53

## Can you answer these questions?

### Fast approximations of Lyapunov exponents in Mathematica

I have $x_i$ sampled IID from $\mathcal{D}$=Gaussian in $\mathbb{R}^d$ with 0 mean and diagonal covariance $H=\operatorname{diag}h$ and need to find the largest value of $\alpha$, such that the ...

numerics linear-algebra
 asked by Yaroslav Bulatov Score of 3

### How to write 2D finite volume solver in a functional approach?

I'm solving 2D poisson problem of a finite volume problem using TDMA. The solution of the problem is given: \[Phi][x_, y_] := x^2 y + x y^2 + 1 The definitions are ...

differential-equations function-construction numerics functional-style
 asked by kpaz Score of 2

### Argument value loss using Listable C-Compiled Function

In my recent studies, I have come across a very strange anomaly with C compiled functions. When I call a function that has the 'Listable' attribute while global variables are accessed through ...

function-construction parallelization compile variable-definitions
 asked by Michael Haring Score of 2
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