34
votes
8answers
2k views

How to generate random points in a region?

The Mathematica 10 documentation was updated for FindInstance adding support for regions. In my use case, I'm trying to sample points in a set of disks: ...
4
votes
3answers
140 views

Help with coding triangular nodes/elements

I'm trying to write a program where it will shoot out the triangle node numbers. For example, in the picture, if we choose to divide this triangle by 5 points, then the program will return out the ...
6
votes
2answers
324 views

Importing multiple images for machine learning classification

I want to create a ML classifier using images just like this example. I have two classes of images in two different folders. Is there an easier way to import all images from both folders rather than ...
3
votes
0answers
85 views

How to solve for exponents in an infinite product?

Say I have a power series, $f(x,y) \in 1 + x\mathbb{Z}[[x,y]]$ Then it admits a unique expansion $$f(x,y) = \prod_{i=1}^\infty \prod_{j=0}^\infty (1 - x^i y^j)^{n_{i,j}}$$ for some integers, $i, ...
6
votes
2answers
157 views

Return value of Reap when using tags

I've noticed a behaviour of Reap that I don't quite understand yet. Suppose I want to Sow several values during a computation. ...
1
vote
1answer
182 views

Horizontally compress a picture with varying compression ratio

I have a function c[x] whose domain and range are both [0,1]. And I have a picture with width W, height ...
11
votes
0answers
519 views

How to export .mtl files for 3D textured objects

I would really like to deploy my textured 3D graphics in the web with sketchfab in my blog. Unfortunately, Mathematica only exports the shape of the 3d graphics, i.e. the .obj file, but omits the ...
2
votes
0answers
252 views

Two problems with NDSolve when using Method -> Projection

I tried to solve a system first order differential equations together with a constraint equation. I use the Method -> Projection to check if the constraint holds ...
1
vote
1answer
258 views

Window ▶ Show Handwriting Input

How might I force Mathematica to display the Handwriting Input menu? Currently I'm on W7 using a Wacom Tablet and unable to find the Handwriting Input option. It doesn't display under Windows>.
6
votes
3answers
419 views

How to count the integer grid numbers defined by inequalities?

I have the following code to show a red area defined by inequalities: ...
6
votes
4answers
1k views

DSolve not finding solution I expected

Try to solve the following ODE via DSolve $$ \left\{\begin{aligned} y'(x)+2 y(x) e^x-y(x)^2 &= e^{2 x}+e^x \\ y'(0) &=1 \end{aligned}\right. $$ The ...
0
votes
0answers
100 views

Lightweight Grid preferences screen stopped working after v10 install

I am getting the following error when I try to open the Lightweight Grid "Preferences" tab... ...
3
votes
1answer
153 views

May I restrict caching to disk when memory runs low? [duplicate]

An hour ago, I had to hard reset my laptop again because Mathematica froze the system again. When import a large file or make a mistake that produces huge arrays with complicated entries etc., I often ...
18
votes
4answers
425 views

Make MapIndexed listable

My goal is to apply MapIndexed to every element of a nested list without destroying the arithmetic operations within the elements. For example, let's start with ...
1
vote
2answers
66 views

How to use the output we see of expression when this expression is inside Dynamic

Consider this example: Manipulate[status = Dynamic[If[a < b, Yes, No]], {a, 2}, {b, 5}] The output of this calculation is ...
1
vote
2answers
690 views

Computing 10-dimensional volume of a 9-sphere [closed]

I'm trying to compute 10-dimensional volume of a 9-sphere with radius r using Monte Carlo. ...
8
votes
1answer
155 views

On using DiracDelta[t] in OutputResposne in version 10. Different result from version 9

I am baffled by this. I was trying to run same example I had working in version 9.01 and found now I get empty plots. The example is here . Here is a simplified version of the above. The same exact ...
1
vote
1answer
138 views

Connect to Windows kernel from Linux computer

I've seen many questions regarding the connection to a Linux machine from a Windows one, but I need to do the opposite. Situation: I have Mathematica on my Linux laptop (...
19
votes
1answer
1k views

Is it possible to insert new colour schemes into ColorData?

Because of the standards in my field, for many plots I need to use (or at least end up using) rather narrowly defined colour schemes, and in particular the Matlab "Jet" scheme, which is well described ...
7
votes
3answers
226 views

Different results with DateRange and LeapYearsQ in Mathematica 9 and 10

With Mathematica 9.0 for Mac OS X x86 (64-bit) (January 24, 2013) one could use DateRange[{2000}, {2010}, "Year"] to achive ...
4
votes
1answer
204 views

How to vary line thickness to add a sense of perspective?

Is there a simple way to vary the line thickness relative to the viewpoint so as to add a sense of perspective? Take for example the following: ...
1
vote
0answers
235 views

Calculate the power spectral density of a Markov chain

I would like to calculate the symbolic power spectral density of a two state Markov process with a symbolic transition matrix characterised by two parameters. I have tried the code below, but it ...
11
votes
2answers
594 views

Map of United States as a 3D histogram

By combining the state data from here and the extrusion code from here I have managed to make prisms of the various US states such as However, the extrusion method looses information about the ...
1
vote
1answer
96 views

How to apply a trigonometric identity to a formula

The product of cosines is given by (Wikipedia): $ \prod_{k=1}^{n} \cos{\theta_k} = \frac{1}{2^n}\sum_{e\in S} \cos(e_1\theta_1+\ldots+e_n\theta_n) $ where $S={1,-1}^n$. How can I apply this to a ...
9
votes
2answers
599 views

Automatically add appropriate prefix to Quantity

Is there a function that automatically adds the appropriate prefix to a Quantity object? For example, I would like a function ...
8
votes
2answers
339 views

FullSimplify giving unexpected result

When I perform a FullSimplify on the list $$ \left\{-\sqrt{5-2 \sqrt{6}},\sqrt{5-2 \sqrt{6}},-\sqrt{5+2 \sqrt{6}},\sqrt{5+2 \sqrt{6}}\right\} $$ I get $$ ...
3
votes
2answers
164 views

Expectation of a composite Markov-Gamma distribution

In a model I have a discrete two-state first order Markov process, defined by a (2x2) transition matrix with two free parameters. If the first state occurs then the process outputs zero for that ...
2
votes
3answers
388 views

How can I apply calculus to functions obtained from NDSolve?

Originally, I asked the question below, but the real underlying issue is as follows: When we solve an ODE numerically, I get the answer like this: ...
2
votes
0answers
54 views

How to expand set of fonts for mathkernel.exe?

If I am running standard Mathematica and I am choosing from the menu Format->Font, I've got everything I need. All necessary scripts are present (Western, Central European,etc.). Whereas If I run ...
2
votes
1answer
314 views

Non-linear curve fitting with multiple parameters and conditional expression

The above integral(Bloch Gruneissen formula) is what i like to fit with my experimental data.I am new to Mathematica. To cross-check the fit results obtained in other software, I try to fit with my ...
2
votes
2answers
154 views

The i-th element of a permutation [duplicate]

I am trying to run something of the form ...
1
vote
1answer
98 views

Attaching functions to movable locators

I'm trying to create a manipulate plot showing the electric field due to a collection of point charges. At the moment I've created such a plot which allows the x and y positions of each charge to be ...
2
votes
1answer
98 views

How to tell NDSolve about known relations of the exact solution

The solution to this system of differential equations: ...
7
votes
1answer
398 views

Smooth convex hull of a large data set of 3D points

I recently needed to deal with a large data set of 600.000 points in three dimensions. My task was to find a convex hull for this data. I have Mathematica 10, so I could use the function ...
9
votes
3answers
508 views

Torus triangulation

I'd like to plot something similar to this but with a triangle instead of a pentagon. Also, I'd like to triangulate the faces, that is, to insert the diagonals for each face of the 3 prisms used. In ...
13
votes
5answers
1k views

To inscribe a circle in a given triangle

I am trying to to inscribe a circle in a given triangle but it isn't working. I've used GeoGebra with this construction and worked but as I'm new to Mathematica I am missing something. It can't be so ...
2
votes
0answers
101 views

Gradient Filter Function

I am trying to understand EXACTLY what the GradientFilter function in Mathematica is doing. As far as I can tell, it appears to be doing a convolution of a first derivative of a Gaussian with the ...
8
votes
2answers
485 views

Export Grayscale Bitmap

I have a grayscale (one channel) image in Mathematica. How can I export it as a grayscale Bitmap? Every single option I tried so far does not have an influence on the Bitmap exported using ...
4
votes
1answer
304 views

ArrayPlot copied to PDF shows blurred mesh [duplicate]

Certain (but not all) images displayed in ArrayPlot, and then copied to PDF, show what appear to be fuzzy mesh lines in white areas. An example is shown below. I ...
5
votes
2answers
178 views

Customizing display of partial differential equations

I am manipulating partial differential equations symbolically, and would like to get the easily readable form $\rho \frac{\partial v}{\partial t}$, leaving variables implicit. Based on suggestions ...
13
votes
5answers
1k views

How to combine one or more rotated graphics objects?

I wish to produce an image with more than one composite graphics objects which have been modified using Rotate. I feel this should not be difficult, but haven't yet found a solution. A simple example ...
6
votes
4answers
150 views

Passing a variable messages list to Quiet

I'm trying to build a Verbose option into some code but I'm having trouble passing to a Quiet statement a variable list of which messages I want to suppress. My ...
12
votes
2answers
265 views

Why isn't Lookup treated like other symbols?

With Mathematica 10, I wanted to overload Lookup using TagSetDelayed, but it doesn't work. For instance, if I define two objects ...
6
votes
1answer
391 views

Installing R packages using RLink on Mac OS X

Is there any updates regarding installing CRAN packages via RLink in Mathematica 10 on Mac OS X? Or are we still stuck with the base R package and that's it? I was able to point to my R distribution ...
3
votes
2answers
136 views

How to define a nestable Baseform function, BaseForm output becomes BaseForm input

Mathematica won't change a number's BaseForm recursively: 63969 // BaseForm[#, 16] & // BaseForm[#, 8] & // BaseForm[#, 2] & Well, I inspected former ...
1
vote
0answers
98 views

V10 interface problems

Has anyone noticed the following? Sometimes when I bring up the Help->Wolfram Documentation there is no text field to type into. When I bring up Find and Replace there are two text fields for Find: ...
5
votes
2answers
153 views

Example of Integrate applying a numerical evaluation N

Here is a minimal example: Integrate[(a[1] + x)^2, {x, 1., 2.}] 2.33333 + 3. a[1.] + 1. a[1.]^2 The problem is that ...
6
votes
3answers
825 views

Laplace: from differential equation to transfer function

First at all, this is trictly related to my own question: How to transform transfer functions into differential equations? How can I transfer my differential equation into a transfer function? For ...
1
vote
1answer
161 views

Strange behavior of function (memory leaks)

I have some funtion: ...
7
votes
4answers
783 views

Solving $L=\frac{3}{2} \sqrt{4 \pi ^2 A^2+W^2}-\frac{\sqrt{5 W \sqrt{4 \pi ^2 A^2+W^2}+6 \pi ^2 A^2+3 W^2}}{\sqrt{2}}+\frac{3 W}{2}$ for $W$

When I solve the aforementioned equation for $W$ or $A$ on Mathematica I get a long and ugly equation in return, namely one of the solutions for $W$ is: (attempt to read at your own health) ...

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