# All Questions

138 views

### How can I monitor and detect when a website has changed?

I'd like to detect when a website has changed, in particular when new products are announced on a site that doesn't change to often. Here's the code I wrote but I don't think it is perfect. Also the ...
505 views

### Left-aligned PlotLabel?

Is it possible to have the text generated by PlotLabel (or any other function) aligned to the left side of the plot instead of in the center?
34 views

### How to implement a set method? [duplicate]

I'm trying to program using object orientation in Mathematica. For this i need to implement get and set methods. Lets consider that we are working with a person class, that have the fields name and ...
642 views

### Simplify Sin[x]/x to Sinc[x]

I have an expression in the form of $\tt \frac{Sin[x]}{x}$ that I would like to simplify to the form of Sinc[x]. I've tried the ...
717 views

### How do I expand a sum?

I have a problem with Mathematica's symbolic manipulations. As an example, consider the following expression: $$\sum _{i=1}^n -2 x_i \left(-a x_i-b+y_i\right)=0$$ How do I get Mathematica to expand ...
351 views

### define the range of Longitude from 0-360 in the World plot from CountryData

How can I change the Longitude range to 0-360 in the such plots? ...
1k views

### World plot without borders between countries

I would like to plot the world map without the countries' borders and just the coastlines (in Mathematica 8). I need to overlap a temperature contour plot on the world map. When I plot country data ...
135 views

### How to evaluate the sum over a hyperplane

I have difficulties in evaluating the following expression: $$\sum_{\small n_1+...+n_{k}=m-k}\; \prod_{i=1}^{k}\frac{1}{(n_i+1)(n_i+2)}$$ I have tried the function ...
280 views

### Why does my matrix lose rank?

I want to check the rank of a matrix for observability, but Mathematica loses a rank if the matrix contains very large numbers. Let's say my matrix is ...
279 views

### How to extract and compute on the diagonal entities of a sparse matrix very fast?

As could be seen in the following code: ...
213 views

### Computing distance matrix for a list

Using functional programming in Mathematica, how can I compute a distance matrix for every element in a list of matrices... The distance would be computed between the item in the list and a "target ...
252 views

### substitution rules for Penrose tiles

This page on W|A shows a nice substitution rule to draw kites and darts. I'd like to implement the rule in Mathematica, so I've drawn the original kite and its replacement (separately). I've also ...
126 views

### Trouble with Replacements [duplicate]

I have the following line of code: Plus @@ Table[p[x], {x, 0, 20}] /. p[x_] -> Boole[MemberQ[{0, 5}, x]] The first part of this produces ...
258 views

### Issues with ColorFunction Scaling when using RegionFunction in VectorPlot

I was plotting a VectorPlot and restricting it to the physically meaningful region using RegionFunction. To my surprise, the ...
96 views

### How to combine file data chronologically via reading numbers in a filename and put it in one list?

Say I have a bunch of files with nearly same filename, eg. data_timestep1, data_timestep2, ... The data itself in one file is ({x1, y1, z1, absolute field value 1}, {x2, y2, z2, absolute field value ...
173 views

### Why does Integrate return a solution that is not defined at a particular point when it actually is well defined at that point?

I am trying to compute Integrate[Sqrt[x^4 + (y - y^2)^2], {x, 0, y}] Mathematica 8 gives ...
402 views

### How can I efficiently write formatted data to a Gaussian Cube file?

I am working with data files that contain information about electronic wave functions. The data format is specified by the quantum chemistry program Gaussian. I need to import the data, manipulate ...
429 views

### What is the difference between prefix/postfix notations and map?

I am new to Mathematica and just experimenting with the different programming constructs. I have been looking at Map and how to evaluate a function for a list of ...
212 views

### Solving a system of equations using subscripted variables

I want to solve this equation: X(i, j) + C*Y(i, j) = Z(i, j) Where ...
632 views

### Using FindInstance to Prove No Solutions Exist

For a small amount of background, I am currently working on an undergraduate research project in Combinatorial Geometry and I'm working on a case analysis for embedding spherical simplicial ...
709 views

### Elegant way to handle columns operations

Inspired by this question from @sjdh and by my recurrent use of columns operations in database sets, I was looking for one way to make columns operations more symetric, so I can handle with matrix and ...
789 views

### How to prove an expression by method of mathematical induction?

I want to prove the expression $$1^2 + 2^2 + 3^2 + \cdots + n^2 = \dfrac{n(n+1)(2n+1)}{6}$$ by method of mathematical induction with Mathematica, but I do not know how to start. How do I tell ...
733 views

### Trying to prove that $x\sin(\frac{\pi}{x})\ge\pi \cos(\frac{\pi}{x})$ for $x\ge 1$

Consider the function f[x_] := x Sin[Pi/x] I want to prove that this function is increasing for $x\ge 1$. This can be done with the first derivative. We have to ...
221 views

### Including two ListLinePlots in a 3D graphic

I have two lists of data which I am plotting on two ListLinePlots. I would like to have these two plots appear perpendicular to each other on a 3D graphic. I have ...
123 views

### How to apply tags to expression terms?

I often see on this site and at the mathgroup the repeated questions on how to rearrange expression that Mathematica "likes" to keep in one form, but the user prefers in another. Consider this trivial ...
99 views

### given n lists, get list of applications of function to n-tuples

Is there a built in function or an easy rule to do the following transformation? H[{A[0], A[1], ...},{B[0], B[1], ...},...] into ...
27 views

### How does Plot evaluate its argument? [duplicate]

I have a list of about twenty InterpolatingFunctions that I'd like to plot. They are interpolations from experimental data (frequency spectra between 100 and 5000 ...
323 views

### Assume function is real valued

I want to create a function returning subscripted symbols and I want these symbols to be assumed real. How do I do that? ...
150 views

### RSolve[{y[0] == y0, y[t + 1] == (1 - (t + 1)/100) y[t]}, y[t], t]

When I evaluate this code: RSolve[{y[0] == y0, y[t + 1] == (1 - (t + 1)/100) y[t]}, y[t], t] I get an RSolve::bvnul error. I don't understand why. Yet, if I ...
966 views

### How can I solve a difference-differential equation?

How do I ask Mathematica to try to solve a recursive relation that defines a sequence of functions? For example, suppose I know that $g_n(x) = g_{n-1}'(x)$ for $n > 0$ and that $g_0(x) = e^{2x}$. ...
2k views

### Visualize Pascal's triangle and other triangle shaped lists

How can Pascal's triangle be visualised like this in Mathematica? Or more generally, how can a 'triangular' list like {{1},{1, 1}, {1, 2, 1}} be visualized in ...
516 views

### NDSolve: Normalizing at every step

Suppose I have an transport equation with an initial conditions: ...
2k views

### How to create this four-dimensional cube animation?

This is a tesseract, a four-dimensional cube, which contains two cubes. Here, each side length of the smaller one is 1, while the side length of the bigger one is 2. How do make I it? I am still ...
994 views

### Series expansion in terms of Hermite polynomials

I am trying to expand a polynomial in terms of orthogonal polynomials (in my case, Hermite). Maple has a nice built-in function for this, ChangeBasis. Is there a ...
423 views

### Do/For loop for plots

I have a lot of points that I would like to get shown on a plot. The problem is that sometimes I only have 2 points while other times i have 10 points. I've tried to make a for loop to create a plot ...
394 views

### Doing local FFT on huge 3D vector data cell mesh and visualizing it spatially?

Simulation type: I'm running a simulation with the OOMMF micromagnetics package http://math.nist.gov/oommf/ where are magnet is represented by a mesh of 3 million cells, it gets excited by a ...
429 views

### Simulating discrete time stochastic dynamic systems

What is the canonical way of simulating discrete time stochastic dynamical systems in Mathematica using the new functionality of Random processes? To take a concrete example, lets consider the ...
621 views

### Does Mathematica solve transfer functions differently to Matlab?

Please note this is an edit to the same question posed a few weeks back: I'm using Mathematica to derive the transfer functions for a three phase AC/DC inverter. Given below is the code for the ...