# Questions tagged [random]

Questions about random number generation and the properties of numbers so generated.

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### Apply RandomReal to list in list in Mathematica

I have a big list: {{1,1,1},{1,1},{1,1,1,1,1,1,1}....{1,1,1,1}} How can I apply RandomReal to every single element in the list?
643 views

### Evenly spaced points on boundary of polygon

I have a polygon and I would like to generate $n$ evenly spaced points along the boundary.
178 views

### Acceptance Rejection Method

I need to generate a random number (real) and then test if this number works on my pdf. if it works i append it to a list. if it doesn't, i reject it. Until now i have done this: ...
138 views

### Generating random coordinates (3D) with constraint

I have been trying to generate random $(x,y,z)$ coordinates (i.e. for 15 ellipsoids) so that they obey following constraints: ellipsoid's length is constant, ellipsoids do not intersect (fulfilled ...
116 views

### Optimize RandomVariate for a $1/x^4$ distribution

I'm working with the following code, where I define a probability distribution proportional to $1/x^4$. ...
86 views

### Generate random point on the external surface of this complex geometry

This is a followup to this question of mine. How do I generate a random point on the most external surface of this complex geometry? ...
37 views

### How to ask FindClusters to return the loss function value in the output?

I have some data points pts as below:- pts = BlockRandom[SeedRandom; RandomReal[1, {100, 2}]]; Now I want to separate ...
1k views

### Generate “nice” random matrix

I don't frequent this community, so please give criticism if this is a poor question. I am trying to make a tool which generates a small (say, $4\times 4$) matrix with integer entries, which has a "...
95 views

### Bizarre error messages when monitoring random integers

I am doing tbl = {}; Monitor[ Do[AppendTo[tbl, RandomInteger[{1, 100000}, 2]], 100000], Length[tbl] ] (well in fact I am doing something less boring but what I ...
102 views

### How to generate a random real under a specified density function?

I want to generate a random real in the interval [0,1] according to the density function f(x) = 2x.
419 views

### Random walk in one dimension — meeting of two particles

I'm new to Mathematica and still teaching all by myself, hope you bear with me. I have the code: ...
116 views

### RandomVariate with a custom distribution [duplicate]

I have a customized distribution and I have to draw some random number from it. How do I use RandomVariate to draw random number from a custum distribution? My naive attempt ...
265 views

### Generate a random pattern with at-most n repeated consecutive elements

I want to generate a random pattern which has at-most n (>= 0) repeated consecutive elements from a sample space. The following example explains what I mean: ...
86 views

### Getting PDF from imported Histogram

So I'd like to create a probability density function from an existing histogram from a program that I use. My input data is of the form ...
179 views

### Sampling “Random” Cyclic / Acyclic Graphs

This is an extension of RandomGraph with specific constraints Where @Histograms wanted to make $n$ random graphs with a specific constraint (in @Histogram's case, having 2 vertices each with exactly ...
134 views

### Uniformly distributed numbers fulfilling conditions

I would like to generate 10 random lists of four elements (t, l, p, ...
104 views

### Understanding Maps and slot

Going through some old code I found this line: ...
697 views

### Smarter Shuffle of a List

I have a 2D matrix representing a keyboard: ...
2k views

### Can this code be changed to run faster?

I've worked for several days trying to get this code to run faster. The imported data is 15MB. ...
81 views

### Evaluation Time of RandomVariate Function

This question is about the runtime of the function RandomVariate. Take a simple normalized Gaussian distribution G on the real line, I tried to generate N random ...
570 views

### Creating a random matrix of no duplicates in both row and column from a given set list of elements

Say I have a list of letters {A,B,C,D,E,F,G,H}, I want to create an $4\times 8$ array where each row must not contain duplicates and each column must also not contain duplicates. Naively writing: <...
150 views

### Is a probabilistic primality test implemented in Mathematica?

Imagine that I need to verify that a specific integer, like $n = 10^{1347}+3049$ is prime. ProvablePrimeQ takes a lot of time, and, even if it will eventually work ...
465 views

### Creating a less random list

I'm trying to create an list like {1,3,2,5,8,7,9}, or {2,1,5,6,4,7,9}, that the elements in each list is sorted in a rough order,...
169 views

### Random particle motion

I have a foundational function that allows me to simulate particles moving in a box according to some movement function. The code is here: ...
55 views

### Looking for a way to run through every time step of a cellular automaton function with random seeds

I have been creating 2D cellular automaton functions in Mathematica and I would like the output to be a graphical representation of the array at each time step. I know I can do this with ListAnimate: ...
213 views

### Getting random points on a mesh region

So I have a region defined by a MeshRegion,like ...
71 views

### Random normalised variable generation

I want to generate 8 random variables (in reality to form 4 complex numbers) such that the sum of the 8 variables squared is equal to unity. The aim of generating such numbers is to perform a quantum ...
148 views

### How do I use the values generated in a for-loop in my first iteration to my next iteration?

This one is somewhat hard to explain, but I'll try my best to. I'm trying to generate a list of numbers (containing only pi/10, 0, -pi/10). Numbers are randomly selected from these 3, where the ...
101 views

### Defining a random potential on the unit square

I'm trying to define a random potential on the 2D unit square. For some fixed j, I want to decompose the unit square into $2^{2j}$ smaller squares with sides length $2^{-j}$. On each of the smaller ...
37 views

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### RandomPoint not evaluating on RegionQ and ConstantRegionQ regions

When attempting to recreate and generalise the MatLab code for Random Vectors with Fixed Sum by first principles I came across a few issue with RandomPoint. ...
118 views

### Random Point on Edge of Cylinder

How can I get a random point on just the curved edge of a cylinder? c = Cylinder[{{0, 0, 0}, {0, 0, 2}}, 2]; RandomPoint[RegionBoundary[c], 50] almost works, but ...
50 views

### RandomChoice inside RandomChoice

I have spent a half hour searching Mathematica.SE for information on this topic, with no luck. The code is: ...
107 views

### Using “RandomFunction” to simulate a Itoprocess with Random initial condition

I have an itoprocess such as: ...
110 views

### RandomReal left randomly unevaluated

Can anyone explain this? In Mathematica 11.1, I have a piece of code that uses RandomReal. Every so often I will throw up a RandomReal::array error. This happens ...
23 views

### Store the output values from a random sample [duplicate]

I am new to programming. I am defining x and y as random samples(as mentioned). Then I define a function h (of x and y). Now I want to get output values of h multiple times at once. I want to store ...
260 views

### Sphere Point Picking in Cartesian coordinates [closed]

I have a vector $\vec{A}(x, y, z)$. Now I want to rotate the vector randomly (x by ϕ, y by ...
364 views

### RandomPoint doesn't seem to work

I define a very simple sphere in 3D as follows: ℛ = ImplicitRegion[(x - 2)^2 + (y - 3)^2 + (z - 8)^2 == 1, {x, y, z}]; Now when I try to sample some 500 points ...
226 views

### Random sample of big big numbers

Consider the following piece of code: m = 2; n = 6; samplesize = 1000; totalsize = 2^(n^m); numbersample = 2 RandomSample[Range[totalsize/2], samplesize]; With ...
196 views

### How do you create a 2D random walk? [duplicate]

I've been trying to create a 2D random walk process for my project. The question is as follows, Create a 2-dimensional random walk process where the walker can move up, down, left, or right. The ...
207 views

### How to implement a Von Neumann neighborhood algorithm to random matrices/grids?

I'm trying to generate square grid templates to drill holes on a plate for a fragmentation experiment. The first part of the experiment I used the program below to generate uniformly random sites for ...
79 views

### How to pick a random points in higher dimensional parametric regions?

I am using a simple code to pick points randomly (uniformly) from a parametric region. This seems to work perfectly with 2D and 3D regions. For instance ...
314 views

### Can I use complex Gaussian random variables in Mathematica?

I have been looking for complex Gaussian random variables and Mathematica, however, I haven't found anything on this topic. Could someone, please, let me know if it is possible to find for example ...
61 views

### How to get a single evaluation of RandomReal in a Block

I want to generate (and eventually sample) a sine wave with a random frequency in the range [½, 1] (i.e. capture somewhere between half and one period of the waveform over the domain [0,1]). The two ...
186 views

### Create a random polymer chain

I want to create a polymer chain (in 2D) of a given length such that: 1. First monomer is at {0,0} 2. All other monomers are in the positive x half-plane 3. The ...
46 views

### RandomVariate without zero

I want to get 10 random numbers drawn from a Poisson distribution with mean 1. But I do not want to include 0 in this. When I do ...
652 views

### Using Random walk on a region [duplicate]

I want to simulate a random walk on two dimension equation using module. Checked the input so the path works ...
43 views

### How to carry out a different function based on weighted probabilities

I am looking to carry out a function based on weighted probabilities I have looked at using If[] and random numbers but ...