Questions tagged [random]
Questions about random number generation and the properties of numbers so generated.
881
questions
6
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3
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Incrementing a random element of an array repeatedly
Consider this code to simulate a simple instance of the coupon collector problem. We initialize an array to {0, 0} and then keep incrementing a random element until we've incremented every element at ...
- 696
0
votes
2
answers
75
views
Appending Random Number to Existing List
My goal is to append random number to list like below.The problem is whenever I try appending a random number, the previously created numbers are changed which I don't know why. How to add a random ...
- 399
6
votes
2
answers
234
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Split a sequence with conditions
I need a function which splits a sequence of arbitrary length
at x random points and which guarantees that each partition (bin) contains a minimum of ...
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1
vote
1
answer
74
views
Unwanted reevaluation in Manipulate with RandomPointConfiguration
Here is a simple illustration of a problem I am encountering. I want to use RandomPointConfiguration inside Manipulate, but it ...
- 548
1
vote
2
answers
169
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How to use first time generated randomly matrix? [closed]
I'm trying to solve one (very little) problem. :)
I've generated 3x3 randomly matrix with
V[i_, j_] := Table[RandomInteger[{-10i, 10j}], {3}, {3}];
Now I want to ...
- 19
0
votes
0
answers
40
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Combinations of distributions to be called with `RandomVariate`
I'd like to manipulate distributions that I'm going to retrieve using RandomVariate; e.g., I would like to take
...
- 153
11
votes
4
answers
964
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How to create a random zonogon?
A zonogon is a polygon that is convex and is made only out of pairs of parallel sides with the same length. Any regular polygon with an even number of sides is an example of a zonogon.
When I use: <...
- 403
3
votes
2
answers
157
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Approximate a Wiener Process by a Karhunen-Loève expansion
I'm trying to approximate a Wiener Process by a Karhunen-Loeve expansion (see slide 20) with the following code:
...
- 2,882
3
votes
2
answers
205
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Fill data points within the boundary established by the given points
I have the following data points:
...
- 135
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1
answer
83
views
2
votes
1
answer
185
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Applying NDSolveValue on a differential equation
I am trying to solve stochastic Schrodinger equation (Schrodinger equation in the presence of Ornstein Uhlenbeck Process)
$$i\frac{d}{dt}\begin{pmatrix}c_1(t)\\ c_2(t)\end{pmatrix}=H(t)\begin{pmatrix}...
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4
votes
5
answers
222
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How to delete the complex numbers which are generated in a list of numbers?
Here I have generated a list of numbers
...
- 135
1
vote
0
answers
106
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Random Seed and Parallelization in Compiled Functions
I am having trouble reproducing a random number from a compiled function with parallelization even with the random seed being set.
Specifically, running the following script should give the same value ...
- 11
3
votes
2
answers
120
views
How can I use replacement rules with randomized values? [closed]
Suppose I have a list that I want to use replacement rules to replace each occurrence of a a given symbol with a randomly selected value, with this choice being randomized for each occurrence.
For a ...
- 1,089
1
vote
0
answers
37
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How can I use RandomFunction to solve an SDE in reverse time?
I am working with a problem of the Ito-stochastic differential form given by
$$\mathrm{d}x=g(x,t)\,\mathrm{d}t+f(x,t)\,\mathrm{d}W,$$
where $W$ is a Wiener process.
I furthermore have to satisfy the ...
- 21
3
votes
2
answers
111
views
Update Random Each Repetition of Animate
I found a solution that's not what I wanted but it will suffice
Thanks - Larry
...
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1
vote
3
answers
135
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Plotting Average Positions of 2D Random Walk
I need to generate a plot that shows the averaged position at n steps of 1000 different random walks that are each 1000 steps long. So far I am using ...
- 11
0
votes
0
answers
24
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Smoothening noisy distributions to learn eigenvalue statistics
I have a problem involving random matrices, in which I'm trying to learn properties of their spectral statistics. The problem I'm having can be boiled down to a list management issue, but I will begin ...
- 647
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1
answer
58
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How to get the time series of colored noise obtained by AudioGenerator function?
In the documentation I found a code that plots a Periodogram.
...
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1
vote
1
answer
84
views
How to get randomly arranged image in Mathematica?
I'm now thinking about randomly arrangement of the imported image.
After importing 2 hand-written images, image1 and image2, I want to make each 5 copys and randomly arrange them in one graph, i.e. ...
- 111
0
votes
0
answers
73
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How to generate points belonging to some region very fast?
Consider two variables Ex,th. th ranges within
thmin=10^-5;
thmax=Pi/2;
while ...
- 4,681
4
votes
1
answer
229
views
Illustrating the central limit theorem
I'm working on this question is from Wolfram Mathematica online course. I tried my best to find the answer, still not getting it right
The question is:
Make a list of histograms of 10000 instances of ...
- 307
1
vote
1
answer
90
views
Why is generating normalized random $1000 \times 1000$ matrices and plotting the eigenvalues so slow?
For each of the distributions $N(0,1)$ and $\pm 1$ equal probability and for each of $N \in \{5,10,20,50,100,200,1000\},$ I want to generate an $N \times N$ matrix with entries chosen from the ...
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1
vote
1
answer
129
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Wolfram Mathematica Monte Carlo for integrals approximation
I wanted to implement the Monte Carlo method for multiple integrals approximation in Wolfram Mathematica. Namely I wanted to let the user insert as input the dimension of the integral and the number ...
- 11
2
votes
1
answer
52
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8
votes
1
answer
289
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Creating a random symmetric matrix with a particular rank
The documentation about LinearAlgebra has a section on Constructing Matrices, but the examples of random matrices using RandomReal don't offer an obvios way to ...
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votes
2
answers
68
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Table generation with random variates inside. Mathematica [closed]
I'm new on this forum, and I'm also a new user of the software Mathematica. For this reason, I'm sorry if my question will be unclear and / or dumb.
I have to make a numerical simulation with random ...
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votes
1
answer
79
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Bad performance of 3D self-avoid persistent random walk with periodic boundary conditions
I'm trying to simulate a self-avoiding persistent random walk with periodic boundary conditions a large number of times. For some reason, the script I've written is extremely slow for self-avoiding ...
- 105
0
votes
0
answers
51
views
Changing permutation dynamically
I am trying to make a visualization of permutation as a graph. With the first compilation of program I want to get random permutation and then be able to dynamically change permutation that I desire ...
- 21
0
votes
2
answers
44
views
Cannot use RandomSample to get a sample bigger than the original [closed]
I have a sample of 300 elements and I need a random vector of size 100000 which consists of random repetitions of the elements of the 300-element sample
I have tried the following
...
- 223
1
vote
1
answer
95
views
Speed up random set partition code
I have managed to construct code for randomly generating a set partition of size n with k parts. Note that the total number of such objects is counted by a Stirling number of the second kind.
The code ...
- 2,449
0
votes
1
answer
66
views
Check if NDsolve solution of nonlinear second order eq. is random
I'm solving second order nonlinear eq. using NDsolve. I'm interested in y'(t) dynamics (plotted below). The thing is - from this solution I'm not sure if we have some randomness or it is just complex ...
- 181
1
vote
0
answers
99
views
How to construct an orthogonal matrix with the elements taken from a uniform distribution?
I want to construct an Orthogonal matrix such that its elements are randomly chosen from a uniform interval $[-r,r]$ in Mathematica. The way I am doing it is by simply constructing a matrix whose ...
- 187
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votes
0
answers
38
views
What is the best memory utilization and efficiency considerations for simulating particles that are randomly created and removed?
I am wanting to run a simulation involving a varying number of "particles" (points defined by 2D coordinates $(x,y)$ within some region). At each time step, there is a probability that a new ...
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votes
2
answers
256
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Randomly colored and randomly sized points in a region
I am trying to show random points with different colors and sizes. However, the following code generates random points with the same color. I want them in different colors.
I think I have a problem ...
- 1,554
3
votes
3
answers
228
views
Plotting a unit length line given its midpoint and an angle
I have generated random 3-tuples: $(x, y, \theta)$ where $\{x, y\}$ is the midpoint of a unit length line and $\theta$ is its angle with respect to the x-axis. Is there a way to plot these lines ...
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3
votes
3
answers
200
views
Randomly pick ten numbers from a table such that no two numbers are on the same row or the same column
I have generated a matrix as follows:
Range[41, 50], Range[51, 60], Range[61, 70], Range[71, 80],
Range[81, 90], Range[91, 100]]) // MatrixForm
I was ...
- 93
3
votes
1
answer
302
views
Stochastic process: Understanding Ornstein Uhlenbeck Process
Recently, I have been trying to simulate a random/stochastic variable that follows Gaussian distribution and also has an exponential correlation function $\left\langle X(t)X(s)\right\rangle= e^{-\frac{...
- 573
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votes
0
answers
79
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How to uniformly distribute data points in all the region in a ListLogLogPlot
I've drawn a listLogLogPlot by generating random numbers. But the random numbers are not uniformly generated in all the region. More points are generated in the higher region than in the lower side. ...
- 135
2
votes
0
answers
88
views
Solving stochastic equation
I am trying to solve, numerically, a classic stochastic Liouville's equation, namely
\begin{equation}
\frac{dA(t)}{dt} = -B(t)A(t)+ {\cal C}(t)
\end{equation}
with $B(t)=\cos(\omega t)$, and ...
- 573
1
vote
3
answers
267
views
How to randomly generate points in a line?
For example,how to randomly generate 100 points in line L:y=x,and x~N(0,1).
Edit:I mean,for point p(x,y),x=t,y=t,t is random variable，and t~N(0,1).Randomly generate 100 points like it.
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1
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1
answer
69
views
How can I calculate the moments of a truncated random variable?
I am using the Moment function to calculate the moments of an exponential random variable.
as follows,
Moment[ExponentialDistribution[3], 9]
However, I need to ...
- 223
4
votes
1
answer
176
views
Why won't my random walk work in a Mathematica Do loop? [closed]
This produces a nice random walk plot:
...
- 599
4
votes
1
answer
70
views
Speeding up RandomVariate with custom probability distribution
I have the defined a custom distribution, which is a Gaussian where the exponent can be any real n greater than 0 (set to actually be >0.5 in use), i.e.
...
- 115
0
votes
1
answer
84
views
How to generate random value under the given distribution fast?
Consider a distribution
distr[EN_, Enu_, mN_] =
Exp[-(Sqrt[EN^2 + mN^2]/Enu)]*Sqrt[(Sqrt[Enu^2-mN^2]/2)^2 - EN^2] Sqrt[
EN^4 - (Enu/4)^4]
where mN is a free ...
- 4,681
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votes
1
answer
294
views
How can CompiledCodeFunctions be optimized and parallelized?
Fast generation of random variates as test case
The earlier question (195435) about performance tuning with regard to fast generation of random variates for a gamma distribution has stirred my ...
- 13k
1
vote
3
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310
views
Weighted random choice from a list
I want to randomly choose one element from a list but preferring elements with small distance from the center of a list.
How to do it properly say with normal distribution? I am not good at statistics....
- 9,903
10
votes
1
answer
693
views
Mathematica or math question: why my own Monte Carlo gives different result from the Mathematica's one?
Consider some function of arguments x,y,z, where the latter have some domain of definition $\mathcal{R}$:
...
- 4,681
4
votes
1
answer
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views
How to speedup evaluation of a random point from an implicit region?
Consider three variables s2,t1,t2, and parameters ma,mb,m1,m2,m3,s.
The domain of definition for s2,t1,t2 is given by the region Region3Particle:
...
- 4,681
1
vote
2
answers
126
views
How can I improve this code?
The code below is working well, but it's very slow in the Manipulate box. I know that the Do and AppendTo parts aren't very ...
- 3,969