# All Questions

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 ...
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 ...
214 views

### Solve Probability of Distribution

Why does this work: Solve[Probability[x <= t, x \[Distributed] NormalDistribution[]] == 0.95 ,t] But this doesn't: ...
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 ...
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 ...
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 ...
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 : ...
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 ...
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 ...
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 ...
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 ...
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 ...
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: ...
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 ...
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 ...
680 views

### Difference between @ and @@

I am confused by the commands @ and @@. From the documentation, I learnt that @@ is the ...
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!
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 ...
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 ...
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 ...
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 ...
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 ...
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: ...
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 ...
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" ...
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: ...
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 ...
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? ...
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 ...
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 ...
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 ...
157 views

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

I noticed in this question, Behavior of GraphicsMeshInPolygonQ with self-intersecting polygons, that Mathematica has some "psuedo-hidden" functionality for allowing one to quickly perform a winding ...
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: ...
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: ...
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 ...
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 ...
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 ...
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, ...
528 views

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

Lets assume we have a system model: ...
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: $$\oint_{\mid z \mid =2}\frac{1-e^z+z}{z^3 (z-1)^2}dz$$
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 ...
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 ...
185 views

### Symbol with Subscript but no quotes in it!

If I use the following function to define me a fancy subscript: ...
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: ...
566 views

### How to rotate the z label in 3D plots

Let's take the following simple and funny case ...
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 ...
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 ...
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,
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 ...