2
votes
0answers
34 views

Covariance matrix estimation when number of variables is larger than number of observations

It is well known that the sample covariance matrix estimator results in a singular matrix if the variables is larger than the number of observations. One solution is to apply shrinkage estimators. ...
0
votes
2answers
76 views

How to define $x^n$ where $x=\pm 1$ and $n\in\mathbb{Z}^{+}$?

I do not know how I can define $x^{n}$ in Mathematica, where $x=\pm 1$ and $n=1,2,3,\ldots$. For even values of $n$ we simply have that $x^{n}=1$. While for odd values of $n$ we have that $x^{n}=x$. ...
3
votes
0answers
74 views

speed up evaluating a listable function

I apologize in advance for the vagueness, but I can't think of a more descriptive title. I am trying to find the average value of the square of BesselJ[0, x] ...
13
votes
2answers
190 views

Exporting Dataset to WDX format fails

I reported this to WRI support. Tracking number is CASE:3368636 Official answer is: Thank you for contacting Wolfram Technical Support. This is a known issue and our developers are working on a ...
1
vote
1answer
43 views

Importing a spreadsheet with infinity values from Excel

I have imported a spreadsheet from Excel that I want to use as an adjacency matrix. I want to use this matrix as the argument in WeightedAdjacencyGraph, so I have ...
4
votes
0answers
37 views

SetOptions does not give expected result with Grid [duplicate]

Chech this example: ...
3
votes
0answers
66 views

DiscretizeRegion of ImplicitRegion too small

I have a 2D function that has some sharp peeks within the my domain. I need to find a tight region that contains these sharp peeks. The following is an example of what I would like to do. An example ...
2
votes
1answer
44 views

Defining a function which takes lists as it arguments and threads over them [closed]

I want to define a function with lists as variables, which has the form like m = Table[2, {i, 5}]; f[x_, y_] = m*x + x*y; x and y are list variables; m is a ...
7
votes
1answer
117 views

Finding the least positive integer satisfying a quantified statement

I'm studying the convergence of the sequence of functions $f_n:[0,1]\subset\mathbb{R}\to\mathbb{R}$ defined by $$f_n(x)=n^2x(1-x^2)^n$$ for $n\in\mathbb{N}$. These functions converge pointwise to the ...
13
votes
4answers
335 views

I have the minimum Y value. I want to find the corresponding X value from the list [duplicate]

I have a very big file and contains data in the format of {x,y}. I got the minimum Y value by using data[[All, 2]] // Min[#] & Now I want to get the X value ...
2
votes
0answers
42 views

NDSolve returns asymmetric solution to a symmetric equation

I am trying to find the potential of a conducting cylindrical electrode by solving the Laplace's equation. Both, the boundary conditions and the equation are symmetric w.r.t. the change $r\to-r$. ...
5
votes
1answer
85 views

Slow-down encountered for RandomChoice in large lists

I was wondering if anyone could help me to speed up this code snippet which creates simple (sparse) networks by preferential attachment. The algorithm adds a vertex and an edge each time interval. ...
7
votes
1answer
79 views

Filling Stacked Graph v.10.1

I used a code very similar to the code posted by Kuba stacked line graph with fragmented data ...
5
votes
4answers
137 views

Create Nested List from tabular data

Im trying to create a nested list from tabular data, then onward into a nested association. I can get part way with the help of this answer but it only works for the first level. Repeated use of this ...
3
votes
1answer
74 views

Partial fraction expansion with complex numbers

$$\text{Apart}\left[\frac{1}{x^4+1}\right]$$ Does nothing. How can I get it to expand it. Sometimes it is useful.
1
vote
1answer
104 views

How can I draw a box with moving particles inside and a hole in one side? [closed]

The idea is to create a simulation for ideal gas motion in a container that have a hole and then find the speed distribution for the gas particles that leave the box through the hole. I have a ...
1
vote
1answer
77 views

How to plot two random functions (Together)

I have ploted the next following jump diffusion model using Mathematica 10 $$X_t=X_0 e^{\sigma W_t+(v-\sigma /2)t}(1+J_1)\cdots(1+J_{N_t})$$ namely, a Geometric Brownian motion with compound Poisson ...
2
votes
1answer
85 views

NDSolve-Problem (Calculating field lines)

I want to calculate the field lines of a quite nasty vectorfield. In general the method works fine - except, one of the components of the VF gets 0 - then NDSolve ...
10
votes
3answers
165 views

Adds a rug representation to plot

This question came to me when I read How convert list of numbers to list of points on x-axis? @Mr.W suggested Interlacing a single number into a long list for the question. @Artes provides a very ...
0
votes
0answers
59 views

Replacing function in Sum

I have this expression, which, after execution, gives these $F[s,r]$ in output. $$ S_{1,1}=\sum _{s=1}^{16} \sum _{r=1}^{16} F(s,r) \text{Tr}\left[G_r.G_1.G_s.G_1\right] $$ Here is a piece of ...
1
vote
2answers
57 views

Using Apply on a function with multidimensional input

I have a user defined function which takes multidimensional input, e.g a function that takes two algebraic variables a and b as well as a matrix m and computes some rule function as: ...
5
votes
1answer
112 views

Set PlotTheme globally?

Can one set a default PlotTheme globally? While I recognize one can make lots of workarounds to sort of do this: Go to ...
8
votes
1answer
138 views

Isometric perspective for Graphics3D

Is it possible to render Graphics3D in an isometric projection? I know that the ViewPoint option can be used for orthogonal ...
1
vote
3answers
57 views

Controlling the evaluation of other arguments in pure functions [duplicate]

I have a piece of code where I would like to do the something like the following: ...
2
votes
1answer
84 views

Three questions about two plots

I used the following code ...
0
votes
1answer
42 views
0
votes
1answer
55 views

Combine ListLinePlot and ListPlot3D using Graphics3D

I want to plot something very similar to what is plotted by @Sjoerd C. de Vries in Can 2D and 3D plots be combined so that the 2D plot is the bottom surface of the 3D plot boundary? I need to combine ...
15
votes
2answers
139 views

HDF5 importing large arrays

I have some computations that output a 300,000,000 element array of long unsigned ints, so about 2.4GB, in an h5 file. Mathematica handles files south of 2GB fine, albeit taking very long to import ...
0
votes
0answers
12 views

Finding parameters of a gaussian mixture model that uses markov models [migrated]

I'm using this paper for reference http://www.cs.cornell.edu/~asaxena/learningdepth/saxena_ijcv07_learningdepth.pdf I could get all the features required but have trouble with the probabilistic model. ...
0
votes
0answers
41 views

Mathematica error code 0x00000171

I'm getting above error code with a Trap 132 indication when attempting an ArrayPlot of a complex 130000 x 2048 matrix. Using Mathematica 9.0.1 with Mac OS 10.10.3 ...
2
votes
3answers
85 views

How to check keys and values in nested Associations?

Considering we have a an association: ...
20
votes
1answer
165 views

Is there any Mathematica functionality enabling its use for the blind?

A colleague of mine has become blind as the result of a sudden medical misfortune. We want to help him to feel useful and active again. We, however, still cannot determine what can be done and to what ...
0
votes
2answers
60 views

Solve returns empty list / running forever

Update: I made a mistake before and corrected the sign in code below in case people wonder what some comments mean. Thank you for those who answered. But I should have said that this is only part of ...
1
vote
2answers
81 views

Why does Mathematica not evaluate the difference recurrence using `RSolve` or `RecurrenceTable`?

Mathematica does not evaluate the following recurrence of two variables using RSolve and only echoes the input: ...
1
vote
1answer
36 views

How to apply different colors to different contours

I have searched the forum, I hope this isn't a duplicate question. I try to apply unique color for every contour line with the same elevation. In short, I want to create a MATLAB style contour plot. ...
12
votes
2answers
723 views

How to fill the space outside of an image after rotating it

I want to rotate this image by -50 degrees, and then fill up the black space around the rotated image with a bluish color. I can't find any documentation/answers that suggest how to do it. (Sorry ...
1
vote
1answer
159 views

Modeling a stellar atmosphere

I'm trying to model a stellar atmosphere using Mathematica. Basically I'm working in a physical and chemical model which combined should give me a profile of the chemical abundance in the atmosphere. ...
8
votes
1answer
100 views

Region computations on FilledCurve (with hole)

How can I obtain a precompiled RegionMemberFunction for this geometry? It contains a hole, and the hole's boundary intersects the outer boundary at one point. ...
2
votes
1answer
84 views
1
vote
1answer
33 views

CellEventActions not working within DynamicModule

So here is some code that successfully displays a slider, the value of a dynamic variable, and cycles through a list of 10 images titled 'imgs' with keyboard commands. ...
1
vote
0answers
34 views

Ubuntu: Dynamics are not working after suspending system

I'm working on Ubuntu 14.04 LTS 64-bit and I'm running Mathematica 10.1. Usually, I don't turn my computer completely off but I'm using the Suspend function which is AFAIK a suspend to RAM. After ...
4
votes
1answer
60 views

WhenEvent used in a PDE to output independent variable

I want to use WhenEvent with a PDE after it has reached steady state. I'm posting a system of 2 equations (my real system has 6) and I'm solving the advection-diffusion-reaction 2nd order PDE. First ...
7
votes
2answers
180 views

How to copy and paste $n$ lines from a text editor to $n$ cells?

If I copy from an external editor to Mathematica notebook a block of lines (with a code) line 1 line 2 ... line n then whole text is copied to a single cell. I ...
-1
votes
1answer
47 views

Need help plotting multiple functions [closed]

a = 0.5 b = 0.33333 r = 1.5 e = -0.33333 f = 1 g = 1 m = 0.00001 n = 0.33334 o = 0.00001 p = 0.000003 DSolve[{ x'[t] == a*y[t] , y'[t] == -bry[t] - x[t] - e - f + g*y[t], z'[t] == ...
6
votes
1answer
90 views

Draw from a given list according to empirical distribution

I have two lists, where each time I have age-income vectors. Given the distribution of age in the first list, I would like to draw a sample with the similar distribution of age from the second list ...
2
votes
1answer
72 views

Extracting a time series from a sound object

After importing a sound file, how can I generate a time series (preferably as an $n\times 1$ matrix) which gives the intensity at equal time intervals?
1
vote
2answers
61 views

InverseWaveletTransform of a list of rules

I want to extract coefficient images from a DiscreteWaveletTransform and replace them by modified images of the same dimensions. However, when I use ...
1
vote
0answers
24 views

TimeSeriesInsert issue with Quantity expressions

This first sample code works as expected: ...
10
votes
3answers
156 views

Association of Associations : how to permute level 1 and level 2 keys?

I have a ragged Association of Association, say : ...
0
votes
1answer
83 views

Traces of products of Gell-Mann matrices in FeynCalc

I am working on an assignment in FeynCalc and I need to evaluate traces of products of two commutators of Gell-Mann (SU(3)) matrices, i.e. I need to calculate the ...

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