Questions tagged [probability]
Consider if your question would be better at stats.stackexchange.com. Probability touches upon uncertainty, random phenomena, random numbers, random variables, probability distributions, sampling, combinatorics.
probability
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Group detection in data sets
Assume a group of data points, such as one plotted here (this graph isn't specific to my problem, but just used as a suitable example):
Inspecting the scatter graph visually, it's fairly obvious the ...
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Efficiently summing log quantities
Working in C++, I'd like to find the sum of some quantities, and then take the log of the sum:
log(a_1 + a_2 + a_3 + ... + a_n)
However, I do not have the quantities themselves, I only have their ...
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Confidence Interval/Margin of Recall or Precision
If I have a confusion matrix that is based upon a sample set, how do I determine the statistical power (confidence margin/interval) of my recall/precision/etc metrics? I know how to do statistical ...
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How can I sample a multivariate log-normal distribution in Python?
Using Python, how can I sample data from a multivariate log-normal distribution? For instance, for a multivariate normal, there are two options. Let's assume we have a 3 x 3 covariance matrix and a 3-...
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Monty Hall Program Simulation (C#)
I am trying to simulate the Monty Hall Problem (because I read from the book Think Statistics that a guy in particular was convinced only after seeing a computer simulation) in C#, the programming ...
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Select x random elements from a weighted list in C# (without replacement)
Update: my problem has been solved, I updated the code source in my question to match with Jason's answer. Note that rikitikitik answer is solving the issue of picking cards from a sample with ...
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Probability of 3-character string appearing in a randomly generated password
If you have a randomly generated password, consisting of only alphanumeric characters, of length 12, and the comparison is case insensitive (i.e. 'A' == 'a'), what is the probability that one specific ...
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Why do the inverse t-distributions for small values differ in Matlab and R?
I would like to evaluate the inverse Student's t-distribution function for small values, e.g., 1e-18, in Matlab. The degrees of freedom is 2.
Unfortunately, Matlab returns NaN:
tinv(1e-18,2)
NaN
...
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Sorting with stochastic comparisions
Given a list where for every pair of elements (A, B) the probabilities P(A > B), P(A < B), and P(A = B) is known, how do you determine the most probable sorted permutation?
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How to calculate derivative of multivariate normal probability density function
Is there any built in function calculating the value of a gradient of multivariate normal probability density function for a given point?
Edit: found this how to evaluate derivative of function in ...
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Generate a matrix of all possible outcomes for throwing n dice (ignoring order)
In cases where order does matter, it's rather easy to generate the matrix of all possible outcomes. One way for doing this is using expand.grid as shown here.
What if it doesn't?
If I'm right, the ...
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Algorithm for O(1) weighted random selection with removal
I'm looking for a weighted random selection algorithm with similar characteristics to the alias method, except where items are removed after they are selected.
For example, I have a bag that produces:...
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Multinomial regression using multinom function in R
I was thinking about posting my question in Cross-Validated, but decided to come here. I am using the multinom() function from the nnet package to estimate the odds of becoming employed, unemployed, ...
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What are the ways of deciding probabilities in hidden markov models?
I am starting to learn hidden markov models and on the wiki page, as well as on github there are alot of examples but most of the probabilities are already there(70% change of rain, 30% chance of ...
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Implement probability distribution function in Java problem
I have a function which is in the form of probability distribution function as below:
Although I discover some lib providing function to obtain the result as the above formula would do; but I am ...
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Probabalistic String Matching in Python
I'm in the process of writing a bot that places bets on the website Betfair using their Python API. I want to place bets on football (soccer) matches when they are in-play.
I've coded an XML feed to ...
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How to determine the number of possible combinations of letters that contain a degenerate substring
I've been racking my brain for a couple of days to work out a series or closed-form equation to the following problem:
Specifically: given all strings of length N that draws from an alphabet of L ...
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Are there any known incidents of UUIDs colliding? [closed]
Has anyone ever experienced a UUID collision in the wild? Anyone heard or read of one happening? Can you provide any details?
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Simulating sports matches in online game
In an online manager game (like Hattrick), I want to simulate matches between two teams.
A team consists of 11 players. Every player has a strength value between 1 and 100. I take these strength ...
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Determine Frequency of numbers showing up in dice rolls
For a game I'm trying to determine the frequency that a certain # will show up at a given # of dice being rolled. I know... that question seems odd. Let me try to explain it with real numbers.
So, ...
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std normal cdf, normal cdf, or error function
Can any of these functions, the standard normal cumulative distribution function, the normal cumulative distribution function, or the error function, be reliably calculated with javascript?
I'd like ...
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How to approach this algorithm question?
A website has a database of n questions.
You click a button and are shown one random question per click. The probability of a particular question showing up at the click event is 1/n.
On average, how ...
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R : function to generate a mixture distribution
I need to generate samples from a mixed distribution
40% samples come from Gaussian(mean=2,sd=8)
20% samples come from Cauchy(location=25,scale=2)
40% samples come from Gaussian(mean = 10, sd=6)
...
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Plotting frequency distributions in python
I have a graph stored in an adjacency list format. I randomly select a bunch of nodes and note the number of neighbors each of them have. I now want to plot the distribution, and the way I do it right ...
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What exactly happens if you delete an object? (gcc) (When double-delete crashes?)
Please note that I don't want to solve any problem with my question - I was thinking about probabilities of things to happen and thus was wondering about something:
What exactly happens if you delete ...
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Proper boolean random generator (Bernoulli distribution)
I'd be curious to know if there is a default random boolean generator in the random C++11 library. I've been using a int generator returning 0 or 1 and then converting to bool but I'm trying to ...
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Kolmogorov-Smirnov test
I'm using the R function ks.test() to test the Uniform distribution of the R random number generator. I'm using the following code:
replicate(100000, ks.test(runif(n),y="punif").
When n is less than ...
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Python: Selecting numbers with associated probabilities [duplicate]
Possible Duplicates:
Random weighted choice
Generate random numbers with a given (numerical) distribution
I have a list of list which contains a series on numbers and there associated ...
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Generate stochastic random deviates from a density object with R
I have a density object dd created like this:
x1 <- rnorm(1000)
x2 <- rnorm(1000, 3, 2)
x <- rbind(x1, x2)
dd <- density(x)
plot(dd)
Which produces this very non-Gaussian distribution:...
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Git hash duplicates
Git allows to retrieve the hash of the commit with commands like:
git rev-parse HEAD
which gives 33b316c
or
git rev-parse --short HEAD
which gives 33b316cbeeab3d69e79b9fb659414af4e7829a32
I know ...
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Select random item from stream in O(1) space
Select an item from a stream at random with uniform probability, using constant space
The stream provides the following operations:
class Stream:
def __init__(self, data):
self.data = list(...
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How can I implement the Kullback-Leibler loss in TensorFlow?
I need to minimize KL loss in tensorflow.
I tried this function tf.contrib.distributions.kl(dist_a, dist_b, allow_nan=False, name=None), but I failed.
I tried to implement it manually:
def ...
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Get random item for array based on different probabilities?
Okay, imagine I'm creating a Pokemon game in JavaScript. I have an object like this...
pokemon = {
"pikachu": {hp: 100, probability: 0.1},
"squirtle": {hp: 90, probability: 0.2}
};
I basically ...
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Forward-leaning random numbers' probability distribution
Say I'm pseudo-randomly picking a number from 1 to 50 every second for 100 seconds, and as time goes on the number picked is more likely to be greater. How could I structure such an algorithm?
For ...
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Probability density function from a paper, implemented using C++, not working as intended
So i'm implementing a heuristic algorithm, and i've come across this function.
I have an array of 1 to n (0 to n-1 on C, w/e). I want to choose a number of elements i'll copy to another array. Given ...
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How to generate normal distributed random numbers in Prolog?
I'm a beginner of Prolog. And I'm wondering how to generate normal distributed random numbers in Prolog.
What I know is using the maybe from library(random) one can set up the probabilities. But what ...
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Simulate samples from a joint cumulative distribution function?
I have a joint density function for two independent variables X and Y. And I now want to sample new x,y from this distribution.
What I believe I have to do is to find the joint cumulative ...
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C: Random walk (Brownian motion) program does not return expected theoretical value. Why?
This is just an experiment based on section 6-3 in "Feynman Lectures on Physics":
In its simplest version, we imagine a “game” in which a “player”
starts at the point x=0 and at each “move” is ...
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Randomly generate a set of m integers from an array of size n
Full Question is:
Write a method to randomly generate a set of m integers from an array of size n. Each element must have equal probability of being chosen`
This question is picked from "Crack the ...
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Efficient Method for Calculating the Probability of a Set of Outcomes?
Let's say I'm playing 10 different games. For each game, I know the probability of winning, the probability of tying, and the probability of losing (each game has different probabilities).
From ...
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Select random row from MySQL (with probability)
I have a MySQL table that has a row called cur_odds which is a percent number with the percent probability that that row will get selected. How do I make a query that will actually select the rows in ...
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Pick random element from list with probability
I Have a list that contains four item (A, B, C, D). Every item has a probability to be chosen. Let's say for example A has 74% of chance to be picked, B 15%, C 7% ,and D 4%.
I want to create a ...
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Sampling from a bounded domain zipf distribution
I'd like to sample from "zipf" distribution from a bounded domain.
That is, assume that the domain is {1,...,N}, I'd like each element in the domain, i, to be chosen with probability proportional to ...
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probability of each terminal node in a directed graph
I have a directed graph G(V,E) and weight w(u,v).
In this graph weight w(u,v) represents how many times the node(v) has visited from node(u). for example(See this for a directed graph image):
1 ...
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Is P(A, B) probability equal to P(A intersection B)?
I have to study some probability fundamentals for implementing a computer vision algorithm. However, I'm confused about the notation and meaning of P(A,B) joint probability and P(A intersection B). ...
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C# game of chance
I am new to C#.
What I am trying to do
I am trying to create a game of chance system here.
Basically this is how it is:
My question: How do I do to accomplish what I am trying to do?
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Time efficient implementation of generating probability tree and then sorting the results
I have some events, where each of them has a probability to happen, and a weight if they do. I want to create all possible combinations of probabilities of events, with the corresponding weights. In ...
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Implementing probability distribution function in Java
I'm trying to implement a probability distribution function in java where it returns the ith entry in the array with probability:
Fi = 6i(n-i) / (n3 - n)
where n is the array length i.e. for an ...
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Designing a random number generator
I am trying to design a random number generator which generates random numbers from 0-11.But I need to design that considering I already have a random number generator which generates random number ...
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Select random row with different probability - SQL
I want select random row with different probability column based:
ID Type
Bike 1
Moto 1
Asus 2
Car 1
Apple 2
John 3
If i do this i will have random probability:
select top 1 * ...
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