1
vote
2answers
155 views

How to select three points $A$, $B$, $C$ from the following list so that the circle passing $A$, $B$, $C$ has centre $(1,2,3)$?

I have the sphere $$(x-1)^2 + (y-2)^2 + (z-3)^2 = 36.$$ From the sphere, I find some points with integral coordinates. And select three points from this list so that the triangles are not right ...
4
votes
2answers
165 views

Finding the maximal `t` at which `u[x,t] == 1`?

Given the smooth function u[x,t] on a domain, how do I find the maximal t at which ...
0
votes
1answer
214 views

Solve Probability of Distribution

Why does this work: Solve[Probability[x <= t, x \[Distributed] NormalDistribution[]] == 0.95 ,t] But this doesn't: ...
16
votes
2answers
292 views

Module trash collection behaviour

I have asked this question before on the Wolfram community forum (http://community.wolfram.com/groups/-/m/t/83845?p_p_auth=Gxoxe65B) but not with great success. Module creates temporary variables of ...
0
votes
1answer
59 views

Using Collect with equations

Is it possible to somehow use the expression that Mathematica has collected once the Collect command has been used? What I mean is, I have an expression like this ...
5
votes
4answers
250 views

How to split a list with respect to its nested sublists?

I have a problem with the following task: having some nested list list = {{k6},{k1,k3,k5},{k7}} I would like to replace all sublists by their permutations and ...
4
votes
4answers
1k views

Finding the area of a circle using monte carlo simulation [duplicate]

I wrote the following code to find the area of the circle $x^2+y^2=1$ using monte carlo simulation : ...
0
votes
0answers
77 views

How can I plot the characteristic polynomial? [duplicate]

For example, I have: CharacteristicPolynomial[m, x] 0.5 + 0.1 x + x^2 But ...
5
votes
1answer
83 views

Does Share have any side effect?

According to the documentation, Share[expr] changes the way expr is stored internally, to try and minimize the amount of ...
3
votes
1answer
562 views

Integral of Lorentzian yields different results depending on when parameter assigments are made

I'm evaluating the integral of a Lorentzian, which I know equals one. First I define the function and evaluate the integral in two slightly different ways. Surprisingly, I do not get the right answer ...
2
votes
1answer
222 views

FindMaximum of loglikelihood in Gaussian Process

I am trying to implement a Gaussian Process and have problems to maximize the loglikelihood because the function consists of a determinant of a matrix that is dependent of 2 variables and the product ...
1
vote
0answers
74 views

Decapitating “explicit” and “implicit” heads

This is a follow up to this question. So far, I named "explicit" heads to those that appear explicitly in the expression. For example, f[x] has an explicit head. I ...
4
votes
2answers
613 views

Why does this integral have a complex component?

I wanted to find the probability of my normally-distributed random variable being at least 15, so I set up this integral: ...
1
vote
1answer
96 views

Not getting the range I want when plotting a function with Show [duplicate]

I have a problem with plotting a piecewise defined function with "Show". My code is ...
4
votes
1answer
156 views

Calculate the covariance of a large matrix

I have to compute the covariance of 50 very large integer matrices (2500x2000 elements). However, according to my estimation this will take around 10 days. Do you have any ideas how to speed things ...
9
votes
3answers
680 views

Difference between @ and @@

I am confused by the commands @ and @@. From the documentation, I learnt that @@ is the ...
1
vote
0answers
50 views

Quit Kernel Shortcut [duplicate]

How could I set a Keyboard shortcut for the Quit Kernel -> Local command? I find really disappointing to open the Evaluation menu any time!
0
votes
0answers
175 views

Linear Stability Analysis Routine. Normal Modes in NDSolve

I want to make the linear stability analyis of a nonlinear system of PDEs. So for example then I want to plot what happens to the amplitudes of the modes. To do that I need to solve my equations with ...
0
votes
1answer
368 views

Solving recurrence relationship using iteration

I am trying to create a Mathematica function that basically splits up a continuous function (in this case a physical potential) into steps (strips as it were) and returns the value of the function at ...
0
votes
1answer
386 views

FindMinimum produces error message

I'm trying to solve a logistic regression problem using Mathematica -- more to improve my Mathematica skills than to solve the problem as I have already solved it using Octave. The problem I am ...
10
votes
3answers
480 views

How to visualize the interior of a complicated 3d plot

I have an external data file (can be downloaded here: link 1 or link 2) which contains a dense grid of initial condition in the (x,y,z) space. I read it with Mathematica and plot these initial ...
1
vote
2answers
133 views

Add a letter to a variable name from a list

Basically I am searching for a way to add the letter u to an existing list of variables {a,b,c,d} to obtain the variable list ...
3
votes
1answer
340 views

Plotting a Gravity-Field [duplicate]

I try to plot a 2D gravity field or something similar in the form like $r/|r|^3$ with the standart builtin VectorPlot function: ...
4
votes
2answers
199 views

Dimension of an algebraic variety

I would like to compute, using Groebner bases, the dimension of the variety defined by a set of polynomials in several variables. In the wikipedia page the method is described, and an implementation ...
0
votes
0answers
120 views

Positioning Labeled points in ListPlot gives unexpected results and errors

Original question can be seen in the edit history.... UPDATE: a simpler example - same "problem" ...
0
votes
2answers
127 views

A function that (also) changes a replacement rule

I'd like to write a function operating on a list, returning a list, but also changing a replacement rule. Let's say I have a list of replacement rules: ...
4
votes
1answer
305 views

Von Mangoldt function

Can anybody evaluate the following sum for me $$ \sum\limits_{n=2}^\infty(-1)^n\left(\frac{\psi(n)}{n}-\frac{\Lambda(n)}{2n}\right) $$ where $\psi(n)$ is the Chebyshev function and $\Lambda(n)$ is ...
0
votes
1answer
138 views

Fourier-Analysis How to display every period correctly? [duplicate]

I want to express a function as a sum of fourier series. I tried the code below. It works. But only get one period (from 0 to 1). How to display every period correctly? ...
0
votes
1answer
113 views

Showing the value a plotted function achieves at the right-most point of the plot domain

I'm plotting results from NDSolve, and I'd like to clip them with their value at the point where the line is clipped. So where the curve ends at the edge of the plot, there would be a number ...
2
votes
1answer
390 views

FindRoot giving false roots with Bessel Functions

I have read in some places about the errors associated with FindRoot, but the closest thing I can find on this website seems to be due to the imaginary unit. I am dealing with what should be a ...
0
votes
1answer
280 views

Code to give center of circle given three points in 2D? [duplicate]

does anyone know how to make a function C(p1,p2,p3)=center of circle that goes through p1, p2, and p3? This is in 2D Sorry this is poorly written but I ...
2
votes
2answers
157 views

Are there built-in functions for testing if a point lies within Graphics3D primitives?

I noticed in this question, Behavior of Graphics`Mesh`InPolygonQ with self-intersecting polygons, that Mathematica has some "psuedo-hidden" functionality for allowing one to quickly perform a winding ...
0
votes
2answers
124 views

Drawing a large set of Graphics3D cylinders provided a set of cylinder specifications in a list

I'd like to draw a large number of 3D cylinders using Graphics3D. My list specifying the cylinders has elements that look like the following: ...
0
votes
1answer
77 views

How can I influence the elements plotted in a BubbleChart depending on the tuple plotted?

In a BubbleChart, how can influence the elements plotted depending on a value in the tuple plotted? I want to create a BubbleChart from the following data: ...
0
votes
1answer
187 views

Run FileSystem Remotely and Front End/Kernel Locally

Is there a way to run both the front end(& kernel) locally while the having Mathematica's filesystem(inode's at minimum) reference another os's filesystem? For example currently I run ...
0
votes
1answer
78 views

Collecting variables from Subscript

I have followings set: t = Transpose[{x[#] & /@ Range[20], RandomInteger[15, 20]}]; Subscript[#[[1]], #[[2]]] & /@ t The code is just to build my set.So ...
0
votes
1answer
111 views

Make the y-axis of a plot be in terms of an arbitrary parameter instead of a number?

Sorry if the title is wordy. Basically what I am asking would probably be easier if I just use an example. Say I wanted to plot f(x) = Asin(x) and have the graph come up with the sine function, and ...
1
vote
2answers
179 views

Opacity and overlapping points on ListPlot3D

I am plotting a dataset on ListPointPlot3D, and in order to give an idea of density of points I used opacity of 0.5. The problem is that that while the opacity of points behind one another is added, ...
8
votes
1answer
528 views

How to calculate the $H_2$ and $H_\infty$ norms of TransferFunctionModels or StateSpaceModels?

Lets assume we have a system model: ...
5
votes
2answers
1k views

Paths integrals in the complex plane

I can't find how to calculate path integrals of complex functions in the complex plane. For example: $$\oint_{\mid z \mid =2}\frac{1-e^z+z}{z^3 (z-1)^2}dz$$
0
votes
1answer
80 views

How to close all other MathKernel before opening the new one?

I use MathLink to call Mathematica from C program. After any opening to Mathematica, I do close the connection. However, I don't know why some connections are ...
2
votes
2answers
118 views

Definite Integral. Perfomance problem

I have a notebook in Mathematica 4. I'm trying to convert it to use in Mathematica 9. One of the problem is the long computation of definite integral. In Mathematica 4 the result of the following code ...
2
votes
0answers
185 views

Symbol with Subscript but no quotes in it!

If I use the following function to define me a fancy subscript: ...
2
votes
6answers
217 views

Manipulating List

I have a list: b={{1, 1}, {2, 2}, {3, 3}, {5, 5}, {6, 6}, {8, 8}, {10, 10}} I want to insert the elements in this list: ...
1
vote
1answer
566 views

How to rotate the z label in 3D plots

Let's take the following simple and funny case ...
5
votes
1answer
109 views

Amount of k-sized not-duplicated subsets of subsets of pair with disitinct sorted integers

I have a list, L, of this kind ($n\in \mathbb{N}$): L=Sort[RandomSample[Subsets[Range[n],{2}],RandomInteger[{1,Binomial[n,2]}]]] S contains any k-sized subset ...
1
vote
2answers
215 views

How to simplify an expression with square roots?

The expression $\sqrt{L^2 M+\sqrt{L^2 (-J^2 + L^2 M^2)}}/\sqrt{2}$,can be simplified into $\sqrt{L}(\sqrt{LM + J}+\sqrt{LM - J})/2$, but how can I obtain this result with Mathematica? That is, how ...
2
votes
4answers
148 views

Get the first positive coefficient in polynomial?

I have Polynomial $F(x) = \sum_{i \leq n}{a_ix^i}$. How to get the first $a_i > 0$? Thanks,
1
vote
0answers
72 views

The number of real values assumed by combinations of complex roots of a decic

Define complex conjugate as the pair of complex numbers $a+bi,a-bi$. Assume you have 5 such pairs and they are the 10 roots $x_i$ of a 10th-deg equation with integer coefficients. In general, how many ...
14
votes
1answer
256 views

How to programmatically remove menu items

I would like to do the opposite of what is described here. So rather than add a menu item I would like to programmatically remove one (or more). So given a knowledge of the structure of the menu *.tr ...

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