# All Questions

186 views

### Problem with function as an argument

I want to write a function like the following: s[u_, v_, x_, val_] := u[val]/NIntegrate[u'[x] v[x] + u'[x] v'[x], {x, 0, 1}] So I can evaluate something like ...
260 views

### NIntegrate inside NSum

Consider the following function with a numerical integration: ...
67 views

### Export expression to Matlab [duplicate]

Possible Duplicate: Is it possible to export the equations from Mathematica to MATLAB? I like to export a Mathematica expression like.... ...
638 views

### Is there any way to obtain an approximate inverse for very large sparse matrices?

I have a very large sparse matrix and I need to obtain its approximate inverse and save it as an sparse matrix too. Any of my efforts as could be seen in what follows fail for large n ...
391 views

### Replacements/Substitutions in Mathematica

I am a new user of Mathematica and have some questions about the simplifications of calculated expressions. I am unable to attach an image of the session, but my Mathematica commands are: ...
128 views

### Prevent front-end from reformatting long fractions while editing

I am editing an expression containing wide fractions (typeset with fraction boxes): But if, while editing the equation, the fraction exceeds some threshold (seems to be approximately the window ...
204 views

### Why does OS X need permission to allow JLink connections each time it starts?

I understand that JLink loads each time Mathematica launches or each time a kernel starts, and that this can require permission from the firewall, if it is enabled but OS X provides settings the ...
149 views

### Mathematica Basic Plotting Question

Is it possible to plot y = x^2 and x = y^2 on the some graph? For some reason, I can't get it to plot the ...
150 views

### Optimization of correlation calculation

How can I make the following line of code run faster? Is there a way to do this calculation as a matrix vs vector than vector vs vector? In the code below, f is a ...
431 views

### Why Can't Mathematica Integrate this?

I have the following problem from a textbook I am trying to integrate: So, following the directions in text, I am required to integrate each function. However, I cannot get Mathematica to integrate ...
515 views

919 views

### FeynArts not working properly

So I have installed all FeynArts folders (from 3.5 to 3.7) with FeynCalc 8.0.1., and none of it is working properly :\ First I load the path to specific FeynArts package (3.5 for instance), then, by: ...
238 views

### Is there a way to globally set when to treat a very small number as zero?

I understand that I can use Chop to force a very small number to be treated as 0 and can use ...
352 views

### Why don't I get numeric values from this Solve?

Solve[ a^2 + b^2 == c^2 && a < 100 && b < 100 && c < 100, {a, b, c}, Integers] gives me this result ...
226 views

### Performance of a Do-Loop of variable length

If I'm changing a basis depending on a (non quadratic) matrix $\mathbf{M}\in\mathbb Z^{d\times k}$ and some $\mu\in\mathbb N^k$, i.e. i have an array a of the same ...
185 views

### Cannot calculate with Dynamic variables in a grid

This is a prototype of a grading scheme. In reality it is bigger. The 10 pts in initPtsPartA comes from the school. The output cell should be deployed as a CDF ...
272 views

### Coulomb/kepler potential dynamics. NDSolve breaks

I've been trying to do a simple dynamics in coulomb potential (electron(s) around a nucleus). My equations break down. I think it's because of 1/0. is there a way ...
141 views

### Force size in pixels of plot area excluding axes and labels

I have a matrix where each element represents a pixel. I want to plot the matrix (possibly with ArrayPlot). To suppress aliasing in the final graphic (which I will ...
305 views

### Add values to a PlotLabel; use text characters for PlotMarkers in DiscretePlot3D

I have a plot like this: Table[Plot[a*x^2/4, {x, 0, 5}, PlotLabel -> "a=" a], {a, 1, 5, 1}] I want to label the plots as ...
539 views

### MySQL Connection Problem

I have a problem with the configuration of the J-Connector plug-in with a MySQL database. Most of the time all works well, but sometimes the connection remains blocked for 2 hours and then it gives ...
136 views

### Error in Compiled function at runtime in spatial competition model

I just did a model of spatial competition between two species with different competitive ability & dispersal rates on a lattice with variables nrs of individuals per site. To speed it up I tried ...
315 views

### Problems getting clean sunrise, sunset, civil, nautical and astronomical twilight data

If in a notebook you enter: ...
572 views

### Interpreting the interpolating function and saving data to plot with external program

So far I have been solving non-linear pdes with NDSolve and then plotting the result with the in-built Plot3D and ...
96 views

### How can I know if a pattern corresponds to a string pattern?

What would be the best way to detect if a pattern corresponds to a string pattern ? An invalid string pattern p would lead to an error in ...
197 views

### Exported graphics texture to eps is too dark

Why is the exported graphics eps file so dark? It looks much lighter (and better) as the Mathematica output appearing the notebook. After running ...
304 views

### How to batch rename a directory of files?

I have a directory of files with the pattern: "some_number.some_name.pdf" I want to remove the "some_number." part from all the ...
289 views

### Mathematica Typing Effect

Here is a Typing Effect in javascript. I could only implement a very simple one: ...
311 views

### Specifying parts from lists for plotting using Show

I have the following data: ...
485 views

### Fluorescence Correlation Spectroscopy Simulation

I am simulating Fluorescence Correlation Spectroscopy which basically involves tracking the random motion of particles in a box with periodic boundary conditions and then calculating their intensity ...
187 views

### Restrict SystemDialogInput to open certain file types

The documentation for SystemDialogInput shows how to restrict the types of files shown. SystemDialogInput["FileOpen",".nb"] ...