# All Questions

254 views

### Matrix multiplication involving MatrixForm [duplicate]

Possible Duplicate: Why does MatrixForm affect calculations? I am doing a matrix multiplication, but not getting the desired output. I am doing the matrix multiplication of $A^{-1}B$ from ...
204 views

### How do I write a ValueQ function that only returns True if there exists an OwnValue?

Reading the comments in this answer has motivated me to request a full solution to part of this problem. What I'd like is an efficient solution that returns True ...
260 views

### Conditional Gathering of lists

Just need a little help with the GatherBy / SplitBy function(s). I have a list of random numbers here: ...
3k views

### Importing from Excel

I'm trying to import a matrix from Excel to Mathematica. My code is: Import["desktop/stproj.xls", "xls", data, 1] The output is some weird stuff about population ...
256 views

### Parallelization of distinct array write access from subkernels

I'm working on an implementation of a multivariate FFT, which is (or at least should be) highly parallelizable due to the row-column-algorithm. However, i can't figure out how to implement that. The ...
535 views

### Is there a convenient way to copy/paste text-interspersed SE code snippets into Mathematica?

Is there a way to copy and paste code snippets from SE to Mathematica if these snippets are interspersed with text? Like e.g. in Morphing Graphics, color and location in both the question and answer, ...
908 views

### Morphing Graphics, color and location

I would like to make a small animation : 1-We start with a random distribution of gray points : ...
223 views

### Arguments to If[] are not evaluated

I got bitten by the following: f[x_] := 3*x; g[x_] := If[Log[f[x]] < 0, f[x], 0]; g[x] Out[11]= If[Log[3 x] < 0, f[x], 0] where I thought the call to ...
1k views

### Fetching data from HTML source

I want to generate a couple of plots/graphs with Area51 statistics. Since Area51 doesn't work with the SE API, I'm forced to find another way to get the information I want. That other way is with ...
238 views

### Setting parts of a list

Suppose I have list a = Range[10] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} in which I want to set some elements to be a list ...
348 views

### How to properly DumpSave & Get Globals symbols inside packages while not touching Global context?

For efficiency reasons I prefer to use DumpSave instead of Save. For ease of access I prefer to save symbols in ...
189 views

### Old values are not freed/garbage collected when you re-evaluate an assignment

For this code: (* Cell 1 *) generate := Module[{x}, x = Range[100 * 1000 * 1000]; x]; (* Cell 2 *) g = generate[]; MemoryInUse[] If I evaluate cell 2 ...
536 views

### How to set the NDSolve method to LSODA

I notice that off all the Method options available for NDSolve[...], LSODA is invoked quite ...
210 views

### presenting a real number as real instead of imaginary

I have an equation which results in an answer of the form $\frac{i a}{\sqrt{c-d}}$ is there any way to get Mathematica to present it in it's real form? like $\frac{a}{\sqrt{d-c}}$ I know that I ...
419 views

### How to get string representation (like repr in Python)

I have a string variable. I want to obtain another string which contains the representation of the string variable content itself. s = "a \n b" I need to get a ...
1k views

### Solve Lagrange multipliers optimization problem

I have two nested solid figure, where $V(a,h,\tau)$ defines the volume and $A(a,h,t)$ defines the surface. The outer solid figure is parametrized in $a_s$,$h_s$ and $t_s$ (they share a common center). ...
722 views

### Formatting a fraction as a mixed number

Is there a command that will take a rational number and rewrite it in a mixed-number-like form? That is, I'd like to apply a command to something like 10/7 and get ...
508 views

### Publishing results obtained in Mathematica

I've been using Mathematica to solve nonlinear partial differential equations for my doctoral research for the last 2 years or so. I am not an expert in Mathematica or mathematics and I am an engineer ...
321 views

### Edge problems in a directed graph

I want to create the following two graphs. So far I tried the following Code ...
11k views

### How to make an inkblot?

How to effectively create a polygon that looks like a realistic inkblot? So far, I could come up with this (borrowing from Ed Pegg Jr.'s Rorschach demonstration): ...
172 views

### Calling a function an unspecified number of times

I would like to be able to call a function an unspecified number of times. That is, I would like the generalization of something like: ...
245 views

### MapThread on a nested Map

A simple problem I am facing is here: ...
242 views

### Easy Way to Create Trellis Plots in Mathematica

I'm trying to do multivariate statistical analysis on a data set and I'd like to quickly visualize my information first using Trellis-like plots. For example, I'd like to create scatterplots for body ...
675 views

### Height-dependent filling color in 3D Data Plots

I would like to have the filling of my ListPlot3D display the same color than the one applied to the data. This question makes sense only in the case of conditional coloring of data (according to ...
507 views

### Avoiding an unresponsive user interface in OS X

I have found that despite Mathematica's numerous updates, each of which have added much functionality, one fundamental issue remains unaddressed: The unresponsiveness of the UI when I make a mistake ...
3k views

### What is so special about Prime?

When we try to evaluate Prime on big numbers (e.g. 10^13) we encounter the following issue : ...
1k views

### Composition: how to make a day and night world map?

Given the following world images: ...
269 views

### Path queries for tree-structured data

Can anyone suggest documentation or tutorials for developing path queries and indices for (XML-like) tree-structured data? Suppose data is organized hierarchically in key->value pairs, eg: ...
253 views

### Manipulate Evaluation Order Problem

I seem to be getting some unintended results from a nested Manipulate that I have not been able to resolve. I boiled down the problem I'm having to a simplified ...
483 views

428 views

### simplifying $\frac{\log x^a}{a} = \log x$

If one makes the assumptions $x>0,a>0$, then $\frac{1}{a}\log x^a = \log x$. Thus, in Mathematica, Simplify[1/a*Log[x^a], {a > 0, x > 0}] returns ...
192 views

### Changing the plot variable inside Plot [duplicate]

Possible Duplicate: Difference in Plot when using Evaluate vs when not using Evaluate Assume one has vector of functions (e.g., vec={x,x^2}). The ...
354 views

### How do I treat elements in a list as variables inside a module?

I want to be able to assign values to a list element inside a module. For example if I have: ...
178 views

### Checking if first derivative is zero at a given point

I have a function V[a_, h_, tau_] := (Sqrt[3]/2) h (Sqrt[3] a + h/3 tau)^2 now I want to check, whether its first derivative is zero in a given point. Say for ...
348 views

### ordering of functional eigenvalues

Is there any order to the symbolic eigenvalues of a matrix returned by the command Eigenvalues[...]? While numerical eigenvalues are listed in descending order ...