6
votes
4answers
910 views

How to apply a function to a list of tuples

trialList = {{0, 24.701}, {1, 24.69}, {2, 24.733}}; f[x_] := x + 1; I would like to apply the function f to only the second ...
5
votes
1answer
268 views

Why does this pattern for combining two lists require triple underscores (___) to work?

I understand that __ is a list of one or more elements, and that ___ is 0 or more elements, but when I try this rule with 2 ...
4
votes
1answer
634 views

Efficient method for inverting a block tridiagonal matrix

Is there a better method to invert a large block tridiagonal Hermitian block matrix, other than treating it as a ordinary matrix? For example: ...
8
votes
2answers
8k views

Make a scatter plot from two lists

I have two lists of values xx = {0.1, 0.3, 0.35, 0.57, 0.88, 1.0} yy = {1.2, 3.5, 4.5, 7.8, 9.0, 12.2} I want to make a scatter plot (list plot) with xx as x ...
1
vote
1answer
81 views

Asymptotic expansion of a list

I am trying to calculate a asymptotic series expansion of a list. ...
0
votes
2answers
676 views

How can I suppress message “… cannot be used as function”?

I'd really appreciate your help. The code gives me a solution, but in the end it says it cannot be used as function, which is not true. Script: ...
0
votes
1answer
198 views

How can I impose a condition on Solve or FullSimplify?

I would like to define a real 3-D vector as, say, v = {x, y, z}, but I want it to have a fixed norm and not necessarily a unit norm. I would like to impose this ...
2
votes
3answers
175 views

Manipulate fails with f[x]=x^k/(1+x^k)

I have this code: Clear[f] f = Function[x, x^k/(1 + x^k)]; Manipulate[Plot[f[x], {x, 0, 5}], {k, 1, 10}] But nothing draws as I move the slider. Am I missing ...
22
votes
1answer
684 views

Why are there two separate MathKernel processes running when I start up Mathematica 9?

When I start the Mathematica 9 Front End, and check the list of running processes, I see two separate MathKernel processes. If I only start the kernel, without a front end, then there's only one ...
3
votes
1answer
1k views

Join a piecewise plot

I wrote some code to get a piecewise plot which is displayed correctly. Now I'd like to join the various parts of the plot, using some kind of interpolation, to get a continuous chart even though it's ...
0
votes
0answers
54 views

Mathematica: How to apply a function to a list of tuples [duplicate]

trialList = {{0, 24.701}, {1, 24.69}, {2, 24.733}}; f[x_] = x + 1 I would like to apply the function f(x) to only the second element of each tuple. How is this ...
21
votes
3answers
3k views

Fastest way to calculate matrix of pairwise distances

It is a very common problem that given a distance function $d(p_1,p_2)$ and a set of points pts, we need to construct a matrix ...
1
vote
2answers
189 views

Solve f'[x]==0 for x

I tried the following: f[x_] := x^n/(k + x^(2 n)); Solve[f'[x] == 0, x] But I got the following response: Solve::nsmet: This system cannot be solved with the ...
0
votes
1answer
190 views

Solving a differential equation for a variable in a function

This may sound like a very trivial question, but I need to solve a differential equation as follows: ...
0
votes
2answers
574 views

Simplifying a trigonometric equation to obtain specific terms

When I try to solve the non-homogeneous differential equation ...
8
votes
2answers
610 views

How to generate a matrix group?

I have three $7\times 7$ matrices (with real entries, lots of zeros) and I'd like to check if they generate a finite group (or, more precisely, if the group they generate is of precise order). Would ...
2
votes
1answer
177 views

How to extract the bin width from a Histogram made with an automatic binning method?

I am using the Scott binning method with Histogram and Histogram3D to plot some data. How could I find out the bin width chosen ...
0
votes
1answer
848 views

Steady states and eigenvalues for a non-linear system:

I am trying to understand a non-linear system of equations, and find their steady states and dynamics. I am noob to understanding Mathematica (I am using version 6, but I have access to the latest ...
8
votes
3answers
1k views

Convex hull of a 3D object?

I am trying to find a convex hull command for a Graphics3D object. Does it exist in Mathematica? ...
16
votes
1answer
203 views

Standard message definition construct

Why are the messages almost always defined like this (at least in packages): If[Not@ValueQ[function::usage], function::usage = "Usage message"] and not just like ...
3
votes
1answer
136 views

Reading RData files without RLink

I am using Mathematica 8. I would like to read some RData files which I have received. I do not currently have an installation of R on the machine with Mathematica.
10
votes
4answers
407 views

How to pass a list of arguments into HoldAll

I have a list of arguments (which in reality is lengthy): arguments = {a, b, c} arguments2 = {a_, b_, c_} f[Sequence@@arguments2] := a + b + c Note: It seems ...
2
votes
1answer
376 views

Evaluate Notebook from .Net

How is it possible to send the whole content of an existing notebook to Mathematica for evaluation by using NetLink/C#?
10
votes
2answers
164 views

Can anyone explain this strange behavior of InputForm?

In Mathematica 9.0.0, when to display the input form of two numbers, I come across maybe a puny problem. In order to focus on the problem, I will put up a simplified version. ...
5
votes
1answer
2k views

Methods for NonlinearModelFit

I am using NonlinearModelFit for a thesis project. I get quite different results if I change the Method to LevenbergMarquardt or QuasiNewton or ConjugateGradient ...
5
votes
1answer
96 views

What happened with the file?

What happened with this file? infile = "\\test data.txt"; outstr = OpenWrite[infile]; instr = OpenRead[infile]; Read[instr, Record]; Close[instr]; All ...
8
votes
5answers
412 views

Efficiently finding the positions of a large list of targets in another, even larger list

I have a big list. It contains nearly 60,000 sub-lists. It's structured like bigList = {{x1,y1,z1},{x2,y2,z2},{x3,y3,z3},.....,{x60000,y60000,z60000}}; I have ...
4
votes
1answer
276 views

ContourPlot from Vector Data

I have data in the form of x, y, vx, vy where vx and vy are components of the velocity vector at point x,y. I want to plot a contourplot of this. How can I do that since contourplot asks for three ...
16
votes
4answers
861 views

Clustering a set of points

I have a set of 2D points in the square defined by {-1, -1} and {1, 1}. These points typically form compact groups. I need to ...
3
votes
0answers
387 views

How to make 3D object smooth?

This thread considers mathematical methods here to make the 3D object smooth but this question consider how to achieve the goal of smoothing a 3D object in Mathematica. I want to get smoother ...
12
votes
1answer
112 views

Is there a callback for notebook exit?

I know that $Epilog is called when Mathematica is exited; is there a callback upon exiting the notebook? If so, what is it?
0
votes
2answers
323 views

Creating an API or Widget based on a Mathematica notebook

I'm trying to create a matrix calculator and graph tools for our website and was wondering if there is a way to create Wolfram API or Widgets based on a Mathematica notebook.
4
votes
1answer
448 views

How do I set the boundaries of the legend for a ListDensityPlot?

I have a 3-d array imported from a text file. One dimension represents time, and the other two represent space. It's basically an array of 2-d arrays of temperature values. I want to plot these values ...
12
votes
5answers
376 views

Faster way to convert triangle list to edge list with no duplicates

I have a list of triangles returned by a Delaunay triangulator, in the following format: ...
1
vote
3answers
517 views

How to revolve a surface about a line other than the $x,y,z$ axes? [duplicate]

I just started working with Mathematica 8 and I'm having trouble revolving a function the way I want. I have to revolve the function $x^2/4 +2$ and $y= 0$ around $y=6$ to form an ashtray, but I ...
5
votes
1answer
950 views

Manipulate (Linux version of Mathematica)

I'm runnning Mathematica 9 on Ubuntu 11.10. After installing CDF player I still have problem (most of time) with Manipulate. Only way I'm able to change value of a ...
5
votes
2answers
258 views

Update a function avoiding infinite recursion

I am quite new to Mathematica and not completely familiar with functional programming. I am currently working with a function (call it foo) and wish to change its behaviour, for example, by adding 1 ...
4
votes
2answers
604 views

Evaluating the integral of $\cos (\theta )\cos\left[\tan ^{-1}\left(\frac{a^2 \tan (\phi )}{b^2}\right)\right]$

I am trying to evalute the following integral: Integrate[Cos[θ] Cos[ArcTan[a^2/b^2 Tan[φ]]], {φ, 0, 2π}] I know that for $a=b$ I should get 0 out of the integral ...
1
vote
1answer
121 views

Only perform a symbolic differentiation once

I want to define a function that involves a differentiation step that Mathematica can do easily, which might be of the form ...
2
votes
1answer
82 views

Numerical integration with OwnValues

Say I have a symbol with an OwnValue a = y And we define an integration like this ...
1
vote
1answer
545 views

Problem using NDSolve

This might be some simple mistake, but I am running out of ideas. I am trying to fit an ODE system to some data. This error keeps appearing NDSolve::nlnum: "The function value {0.299812 - ...
9
votes
2answers
347 views

How can I get the right hand side of a delayed expression?

Imagine there is a given function f, defined with SetDelayed, say f[x_] := Sin[x]^2 + Cos[x]^2. Is it possible to get rhs of ...
1
vote
1answer
457 views

Substituting solution from Solve into the equation and making a plot

I want to solve an equation and substitute it into a Plot expression. My code looks something like this a[b_, x_] := bx + 1; sol = Solve[(1 + b)x + 1 == 0, b] I ...
4
votes
2answers
303 views

How can I change a Slider's appearance?

I am using Mathematica 9.0 and Windows 7. I want to create a Slider that looks like the following: I tried the following: ...
0
votes
0answers
43 views

Define a Plot3D function with custom options [duplicate]

I am trying to define a Plot3D function with custom options, following (this previous SE question), but I'm running into a brick wall. I've narrowed the problem to the following 'toy' code: ...
1
vote
1answer
221 views

Automating sequential import of data from web

I am trying to import data from multiple web pages hosted by a single online source. The data is posted by the source as one data set per web page for each week of the year. I would like to import the ...
0
votes
1answer
184 views

Alleviating a bottleneck involving a function call with symbolic derivatives

I have a bottleneck problem involving a function call with symbolic derivatives. I don't have much experience with Mathematica (or any dynamic language) and I'm certain that the way I've set this up ...
0
votes
2answers
556 views

Using Mathematica to find poles of Gamma functions

I am concerned about the expression on the RHS of equation A.5 (page 19) in this paper: $$\int\frac{d^d ...
4
votes
2answers
316 views

Mathematica averaging a big list of large images

I have a list of several hundred images, and I want to average the list to get a single image. Each image is 12bit TIFF with 2048*2048 pixels, and I am using the following to do the job: ...
11
votes
3answers
4k views

Solving a time-dependent Schroedinger equation

I want to solve the time-dependent Schroedinger equation: $$ i\partial_t \psi(t) = H(t)\psi(t) $$ for matrix, time-dependent $H(t)$ and vector $\psi$. What is an efficient way of doing this so ...

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