Questions tagged [sampling]
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56 questions
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Selecting elements from sublists (with removal) subject to constraints on the sublist choice
My problem is a little difficult to explain so I'll exhibit with a couple of examples.
Given the following nested list - {{5,13},{5,11},{23}} - imagine the sublists are urns with balls numbered with ...
- 307
0
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2
answers
180
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Sampling irrational numbers [closed]
I'm sorry that my unclear statement has caused some misunderstanding. This edit was just to stop misunderstanding, Keep Closed.
I don't know if there is another software with a better fit for this ...
- 459
0
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0
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21
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Simulating data from a piecewise pdf occasionally returns an error [duplicate]
In the following code, I generate data from a piecewise PDF. Usually, I get a sample size of ns, but sometimes I get an error message:
Error: RandomVariate::unsdst:...
- 9
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0
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92
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2
votes
1
answer
121
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Fast sampling from Fermi-Dirac distribution under specific conditions
This question is a continuation of the following one.
Let us assume a Fermi-Dirac (FD) distribution (times $p^{2}$):
...
- 5,963
1
vote
1
answer
133
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How to quickly sample from the following distributions
Consider the following distributions:
...
- 5,963
1
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1
answer
100
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How to compile the following code (sampling from a distribution)?
Consider the following code:
...
- 5,963
0
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0
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61
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How to quickly sample points according to the given distribution?
Consider the following points sampler:
...
- 5,963
0
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1
answer
84
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Resampling the points with a constraint [closed]
I have a list of npts elements energies obeying some arbitrary distribution. By performing some operation many times, it would ...
- 5,963
2
votes
0
answers
62
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Why RandomSample fails and how to fix this?
Consider the following sampling:
weights = 10^RandomReal[{-13, Log10[35]}, 499500];
vals = Range[Length[weights]];
randomvals = RandomSample[weights -> vals];
...
- 5,963
0
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1
answer
84
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How to select non-repeating pair of numbers?
Consider the following combinations of integers comb, where the integers range from 1 to n ...
- 5,963
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0
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130
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How to quickly generate the values satisfying the given condition?
Consider some domains in variables th, z and some condition cond defining the domain of a ...
- 5,963
4
votes
1
answer
235
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How to quickly sample points from the given PDF data?
Consider some data (distr.dat). It is a tabulated PDF: x, y, z, PDF[x,y,z], where x is some parameter (and the integral of ...
- 5,963
1
vote
1
answer
169
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Pick random value based on list of probabilities
I'm pretty sure this must have been asked before, but I can not find the duplicate.
Given a list of values with their probabilities
...
- 1,451
2
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2
answers
196
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How to sample from a `MultinormalDistribution` with a positive semidefinite covariance matrix?
I'm trying to sample from a Gaussian process (GP) following these tutorials:
https://peterroelants.github.io/posts/gaussian-process-tutorial/#Sampling-from-prior
https://stephens999.github.io/...
- 165
2
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3
answers
138
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0
votes
2
answers
46
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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
...
- 243
4
votes
1
answer
74
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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
6
votes
4
answers
899
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Finding the periodicity (or wavelength) in approximately periodic data irregularly sampled
I have irregularly sampled data that looks as in the picture.
Is there a function in Mathematica that allows me to find an approximate or average period or wavelength?
I know beforehand that the data ...
- 647
0
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1
answer
84
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Is there a difference between generating and loading data?
EDIT-1
This is a minimal example where an error occurs after 44538 samples generated in d1 upon importing as d2. Note that if <...
- 243
4
votes
2
answers
225
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Is there a way to generate a data-driven Monte Carlo sample from a histogram?
I have a vector with 50 elements. These are values of a random variable. I have represented the data as Histogram[RandomVariable1Histogram]. However, I need to ...
- 243
4
votes
1
answer
158
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Reverse engineer visualizations to compactly extract underlying data
TL;DR
How to implement in mathematica a tool such as
WebPlotDigitizer by Ankit Rohatgi
which would allow us to trace automatically curves
from either (randomly ordered) data or imported images.
...
- 23.1k
4
votes
2
answers
235
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Smart under-sampling of a large list of data points
I have dielectric functions of materials as lists of value pairs {{x1, y1}, {x2, y2}, ...} and unfortunately some of them are quite long, which is a bother in ...
1
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0
answers
61
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1
vote
1
answer
69
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Select a subsequence of a sequence according to tosses of a biased coin
I have a sequence, from which I would like to select a subsequence, each term of the original sequence being included in the subsequence with probability $p$, independently of the other terms. That is,...
- 1,445
1
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2
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258
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Evaluate function at "good" points used by Plot in numerical problems
Plot function with option Mesh->All shows how mathematica evaluates function to make it most optimal for plotting.
I'd like to evaluate some physical function in ...
0
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2
answers
82
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How to get a list of exponentially distributed points sampled in a range
I want to get 256 points exponentially sampled in a range, and then get its histogram.
If I plot PDF, I get the following:
...
- 157
3
votes
4
answers
351
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2
votes
1
answer
145
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How to extract colors from ColorsNear?
Is there any way to get a discrete list of samples from the ColorsNear function?
I have tried
...
- 477
0
votes
1
answer
183
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Sampling two integer lists of given sizes from a distribution that have equal sums
(This question emerged from discussions in this post.)
Context and code sample:
I am trying to figure out if there is a way to generate two $a$ and $b,$ comprised of $n_a$ and $n_b$ integers which ...
user52181
1
vote
2
answers
78
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Sampling an inequality over multi-dimensional space
Let's say I have two functions $f(x,y,z), g(x,y,z)$. I would like to know the probability that $f(x,y,z) < g(x,y,z)$ over some defined, numerical ranges of $x, y, z$.
Any thoughts on how to do it ...
- 173
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2
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350
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Plot, sampling, and why it does not display for some ranges
The following gives an empty plot on V12 under Windows 10:
...
- 150k
5
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2
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515
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Why does plot not show where Piecewise function is not zero?
From my user point view this looks like bug. But I am not an expert.
f[x_?NumericQ]:=Piecewise[{{1,x==1},{0,True}}];
Plot[f[x],{x,0,1}]
Does not show ...
- 150k
1
vote
1
answer
195
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Random sampling of a discrete distribution in NetGraph
Within a NetGraph I would like to use the output of a softmax layer, interpreted as a probability distribution, to sample a "next token". Since this is done inside an RNN structure, I cannot do this ...
- 11
1
vote
2
answers
361
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Multiple unique random samples?
I'm trying to produce $n$ random samples from a list, but not all samples, and I'd like the samples to not repeat in the same execution of the command. If I'm not mistaken, something like ...
- 343
2
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4
answers
819
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How to generate a matrix with certain conditions
I want to generate a $n \times n$ matrix.
I want the diagonal entries to be all 0
I want a random choice of matrix elements with 0 or 1.
The probability of having a 1 as a matrix element is $1/m$ and ...
- 21
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1
answer
247
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How do I extract data points from an audio plot at a constant spaced time interval?
AudioPlot[Audio[File["Downloads/1_mp3.wav"]]]
data = Cases[AudioPlot[Audio[File["Downloads/1_mp3.wav"]]], Line[x_] :> x, Infinity]
This code can extract data ...
- 3
1
vote
2
answers
195
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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:...
- 101
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votes
1
answer
59
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ProbabilityDistribution fails for square root
I would like to sampling data from a distribution Sqrt[x^2 + y^2].
I used the code as follows:
...
- 1,131
0
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1
answer
120
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Speeding up Module
I am working on the Ising 2D model in Mathematica and this is currently my Metropolis sampling function:
...
- 11
4
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2
answers
187
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Filtering data with timestamps
How to apply filter to data that was sampled in certain moments of time? Examples from documentation deal only with uniformly sampled data:
...
- 999
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3
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142
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Sample the data with equal step size
I have the data below. I would like to sample with equal step size. For simplicity lets try unit step size. Here is the desired result. Find the first time exceed the unit time step, and take lower ...
- 10.9k
5
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2
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240
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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 ...
- 588
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3
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407
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2
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1
answer
89
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Looking for an estimator for non-linear statistics
Goal
We sample $n$ individuals with replacement and measure their trait values $x_i$ for all individual $i$. The variable $x$ is bounded [0,1].
Let $\mu$ be the ...
- 1,155
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0
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89
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Problems with sampling
Let $t\ge 0$ and let $f_{s}(t)$ be the sampled version of $f(t)$.
If $$f(t)=\begin{cases}\int_{0}^{t}\exp\left(-\frac{1}{1-s^{2}}\right)\,ds,&|s|<1,
\\ 0,&\text{otherwise}.\end{cases}$$
I ...
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votes
4
answers
3k
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How to sample points randomly below a curve? [duplicate]
How can I randomly select 1000 points uniformly from the shaded area below the plotted curve?
Plot[1/π Cos[θ]^2, {θ, 0, 2 π}, Filling -> Bottom]
- 1,131
5
votes
2
answers
331
views
Generate multiple integer variables with constant sum
I have asked similar question three day ago[The old question]. it was incorrectly marked as duplicated. This time I make this question more general and closer to reality.
I want to build a model of N ...
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39
votes
4
answers
2k
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How to implement the sample-point process like the built-ins of Mathematica?
Consider this:
pts = {{0, 0}, {1, 1}, {2, -1}, {3, 0}, {4, -2}, {5, 1}};
f = BSplineFunction[pts]
I can use ParametricPlot to ...
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7
votes
1
answer
384
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Draw from a given list according to empirical distribution
I have two lists, where each time I have age-income vectors. Given the distribution of age in the first list, I would like to draw a sample with the similar distribution of age from the second list (...
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