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Questions tagged [random]

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

2
votes
1answer
59 views

Perpendicular chord lengths from the boundary points of an arbitary 2D shape

Let's generate an arbitrary convex domain with smooth boundaries: Graphics[BSplineCurve[{{1, 4}, {5, 3}, {9, 4}, {5, 5}, {8, 7}}, SplineClosed -> True]] I'...
11
votes
2answers
354 views

On random numbers extracted from NormalDistribution by two different methods under the same seed

I've encountered the following situation within various trials. Why does such a difference arise between bulk sampling and one-by-one sampling? ...
19
votes
5answers
1k views

Sisyphus Random Walk

A Sisyphus Random Walk evolves as follows: With probability (r) you advance the position of the walker by +1. With probability (1-r) the walker resets at x0 = 0. To simulate the probability of reset ...
1
vote
1answer
42 views

How to take a point randomly from a region [duplicate]

I want to take some points randomly by the limits above, I had try to use FindInstance method but it always out (0,0) ...
7
votes
5answers
998 views

Survival Probability for Random Walks

The Survival Probability for a walker starting at the origin is defined as the probability that the walker stays positive through n steps. Thanks to the Sparre-Andersen Theorem I know this PDF is ...
9
votes
2answers
95 views

Controlling the randomness of DropoutLayer

How can I control the randomness of DropoutLayer in order to get the same result after each execution? For example: ...
5
votes
2answers
85 views

Obtain the current value of the seed used by the random number generator

I would like to be able to do something like the following pseudocode: ...
3
votes
4answers
542 views

Random Six Character Strings Without Collisions

I want to generate a random list of six characters that only contain characters from "0...9" and "A...Z". For this I can define ...
5
votes
2answers
246 views

Record Statistics for Discrete Random Walks

I code a random walk of length 100 drawn from a LaplaceDistribution: Accumulate[RandomVariate[LaplaceDistribution[0, 1], 10000]] I am having trouble counting the ...
1
vote
2answers
102 views

Sampling data from numerical values of density distribution of nucleons

How could i sample my data which follows distribution if i have only numerical values of density distribution as an example data attached as in picture I tried but do not know how to do it. The data:...
0
votes
2answers
80 views

2d-RandomWalks with N steps and fixed distance between first and last point

community, I'm trying to figure out a way how to create a 2d list simulating a N-Step-Randomwalk with a fixed distance between first and last point. I already got the RandomWalk with the step size 1: ...
5
votes
0answers
72 views

Random number generation within Compile and Parallelization->True

According to this thread RandomChoice is a compilable function. I use it to generate random numbers in a compiled function with parallelization enabled. I wrote ...
4
votes
6answers
337 views

Randomly distribute numbers to lists

I have 4 empty lists. I would like to randomly distribute numbers from 1 to 10 to these 4 empty lists. How can I add integers to lists randomly? For example: ...
3
votes
3answers
252 views

Sum of Random Integers

I am trying to get a list of numbers with at least 1000 sums as possible, using random numbers from 1 to 10. But I don't want to get blank list output. How can I only get a list of numbers greater ...
0
votes
3answers
36 views

How to create 2 lists of RandomIntegers based on condition?

How do i create 2 lists of RandomIntegers that are the same at certain points based on a condition. For example there are three lists: List A List B List C List C already exists. I am trying to ...
2
votes
0answers
81 views

How to match random number generator to R?

Although I know the algorithm that R is using for pseudo-random numbers I am unable to match the generation of random numbers. ...
3
votes
1answer
129 views

Generate a smooth random function (2D curve) with endpoints specification?

Here is a PDE example, adapted from Wolfram Documentation: ...
2
votes
0answers
51 views

How do decrease uncertainty of Monte-Carlo integration?

I have some function of many arguments and need to integrate it over the region given by the products of Heaviside theta functions. Namely, I write, say, ...
1
vote
1answer
41 views

How to select random number of elements from a list?

Assume that I have a list a = {1,2,3,4,5,6}; and I want to have a function that outputs a subset of the list such that with probability p=0.2 each element will ...
0
votes
0answers
54 views

Random points from an image using a BernoulliDistribution

I am a Mathematica newbie. I need to sample random points from an image which I have stored in a variable img as: ...
0
votes
1answer
107 views

Why does Monte Carlo integration underestimate my integral as integration range increases?

I'm having a huge problem with Monte Carlo integration. This simple example adequately shows the problem. ...
2
votes
1answer
46 views

Matrix Randomization

Is there a way to take a 20x20 array and replace 2 random parts of this array with a 2x2 matrix? I've tried rvalues = ConstantArray[r, {20, 20}]; to make the ...
0
votes
1answer
57 views

Negative values with RandomVariate

I am using the following code to generate some random number from a custom distribution: ...
0
votes
1answer
45 views

Am I using RandomVaraite and ProbabilityDistribution correctly?

The following code does not produce an output on my Mma (version 11.3 for Windows) ...
6
votes
2answers
133 views

How can I get new random values with each blank in ReplaceAll?

Is there any way to get different values for different blanks with ReplaceAll[]? For example, I would like to do something like: ...
19
votes
3answers
1k views

Efficient way to simulate thousands of Markov chains

I am currently trying to simulate relaxation of a protein population while maintaining the stochastic properties of the system. For this, I used a Markov chain to describe the temporal evolution of ...
6
votes
3answers
227 views

How can I delete a random part of an expression?

I have the expression: Times[0.19157500241430547,Power[Plus[0.7235014213631388,k,Times[-1,Power[m,c]]],Times[g,z]]] Also represented as: ...
5
votes
3answers
150 views

Improving the run time of random walk simulation

One of our professors told us that during his thesis he used Mathematica in simulating it since it is about networks, I don't know how he did it but all I know is he said it took about two weeks to ...
4
votes
3answers
139 views

Construct Distribution Histogram From Random Variable

Given a Beta Random Variable $X$ with parameters $\alpha, \beta$ and a positive constant $n$, suppose I am interested in the distribution of: $$Y:=\lfloor nX\rfloor$$ Suppose I want a histogram ...
2
votes
1answer
69 views

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?
11
votes
5answers
501 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.
2
votes
1answer
84 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: ...
3
votes
0answers
61 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 ...
3
votes
2answers
90 views

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

I'm working with the following code, where I define a probability distribution proportional to $1/x^4$. ...
0
votes
1answer
84 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? ...
1
vote
0answers
31 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[123]; RandomReal[1, {100, 2}]]; Now I want to separate ...
4
votes
2answers
266 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 "...
1
vote
0answers
93 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 ...
3
votes
1answer
65 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.
5
votes
1answer
386 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: ...
1
vote
0answers
39 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 ...
6
votes
3answers
238 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: ...
1
vote
1answer
61 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 ...
4
votes
1answer
120 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 ...
5
votes
3answers
127 views

Uniformly distributed numbers fulfilling conditions

I would like to generate 10 random lists of four elements (t, l, p, ...
14
votes
5answers
608 views

Smarter Shuffle of a List

I have a 2D matrix representing a keyboard: ...
7
votes
2answers
1k 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. ...
2
votes
1answer
38 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 ...
0
votes
0answers
35 views

Finding vectors admitting to the same value of a given function

Given a vector function $f(\vec{v})$ where say $\vec{v}=(x,y,z)$ is a $3$ dimensional vector. How does one find a large number of random $\vec{v} \in \mathcal{W}$ from a region $\mathcal{W}$ that ...
8
votes
3answers
106 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: <...