Is every probability distribution
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2
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Say I have some arbitrary $N$-dimensional probability distribution $P$.
I'd like to create a deterministic function that accepts a vector of $N$ uniformly distributed numbers and generates an $N$ element vector where the elements of this vector are distributed according to $P$.
Is this always possible?
probability statistics
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up vote
2
down vote
favorite
Say I have some arbitrary $N$-dimensional probability distribution $P$.
I'd like to create a deterministic function that accepts a vector of $N$ uniformly distributed numbers and generates an $N$ element vector where the elements of this vector are distributed according to $P$.
Is this always possible?
probability statistics
add a comment |
up vote
2
down vote
favorite
up vote
2
down vote
favorite
Say I have some arbitrary $N$-dimensional probability distribution $P$.
I'd like to create a deterministic function that accepts a vector of $N$ uniformly distributed numbers and generates an $N$ element vector where the elements of this vector are distributed according to $P$.
Is this always possible?
probability statistics
Say I have some arbitrary $N$-dimensional probability distribution $P$.
I'd like to create a deterministic function that accepts a vector of $N$ uniformly distributed numbers and generates an $N$ element vector where the elements of this vector are distributed according to $P$.
Is this always possible?
probability statistics
probability statistics
asked 2 days ago
gigalord
253
253
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1 Answer
1
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oldest
votes
up vote
1
down vote
accepted
If $N=1$ then it is always possible.
Let $$ Xsim F, $$
there exists $$F^{-1}(u)=inf {xin mathbb{R}colon F(x)ge u}$$ where $0< u<1$. Thus $$ F^{-1}(U)sim F$$
with $Usim Unif(0,1)$. This method is called inverse transform.If $N>1$. Let $$ X=(X_1,X_2,dots,X_N)sim F $$
where $$F(x_1,dots,x_N)=mathbb{P}(X_1le x_1,dots, X_Nle x_N).$$
If $X_1,dots,X_N$ are independent, then $$F(x_1,dots,x_N)=mathbb{P}(X_1le x_1)cdots mathbb{P}(X_Nle x_N)=F_{X_1}(x_1)cdots F_{X_N}(x_N).$$
Thus is possible to simulate each $X_i$ by inverse transform method and so
$$ (F_{X_1}^{-1}(U_1),dots,F_{X_N}^{-1}(U_N))sim F$$
where $U_1,dots,U_N$ i.i.d. with $U_1sim Unif(0,1)$.
If $X_1,dots,X_N$ are dependent then a procedure that takes this into account is necessary.
So the sufficiency condition here is that $F$ is invertible?
– gigalord
yesterday
Yes, although this is a very strong hypothesis, and in practice difficult to achieve. Also, note that when $N = 1$ we use a generalized inverse, and even this method is not widely used in practice. In practice, Markov Chain Monte Carlo is used to simulate a complex distribution.
– Daniel Camarena Perez
yesterday
In the one-dimensional case the "probability integral transform" is used quite routinely. It's especially easy to implement in the discrete setting, where there are also alternatives that avoid the need for a binary search lookup (by using some preprocessing).
– Ian
yesterday
An example with dependence is a Markov chain columbia.edu/~ks20/4703-Sigman/4703-07-Notes-MC.pdf
– Daniel Camarena Perez
2 hours ago
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
1
down vote
accepted
If $N=1$ then it is always possible.
Let $$ Xsim F, $$
there exists $$F^{-1}(u)=inf {xin mathbb{R}colon F(x)ge u}$$ where $0< u<1$. Thus $$ F^{-1}(U)sim F$$
with $Usim Unif(0,1)$. This method is called inverse transform.If $N>1$. Let $$ X=(X_1,X_2,dots,X_N)sim F $$
where $$F(x_1,dots,x_N)=mathbb{P}(X_1le x_1,dots, X_Nle x_N).$$
If $X_1,dots,X_N$ are independent, then $$F(x_1,dots,x_N)=mathbb{P}(X_1le x_1)cdots mathbb{P}(X_Nle x_N)=F_{X_1}(x_1)cdots F_{X_N}(x_N).$$
Thus is possible to simulate each $X_i$ by inverse transform method and so
$$ (F_{X_1}^{-1}(U_1),dots,F_{X_N}^{-1}(U_N))sim F$$
where $U_1,dots,U_N$ i.i.d. with $U_1sim Unif(0,1)$.
If $X_1,dots,X_N$ are dependent then a procedure that takes this into account is necessary.
So the sufficiency condition here is that $F$ is invertible?
– gigalord
yesterday
Yes, although this is a very strong hypothesis, and in practice difficult to achieve. Also, note that when $N = 1$ we use a generalized inverse, and even this method is not widely used in practice. In practice, Markov Chain Monte Carlo is used to simulate a complex distribution.
– Daniel Camarena Perez
yesterday
In the one-dimensional case the "probability integral transform" is used quite routinely. It's especially easy to implement in the discrete setting, where there are also alternatives that avoid the need for a binary search lookup (by using some preprocessing).
– Ian
yesterday
An example with dependence is a Markov chain columbia.edu/~ks20/4703-Sigman/4703-07-Notes-MC.pdf
– Daniel Camarena Perez
2 hours ago
add a comment |
up vote
1
down vote
accepted
If $N=1$ then it is always possible.
Let $$ Xsim F, $$
there exists $$F^{-1}(u)=inf {xin mathbb{R}colon F(x)ge u}$$ where $0< u<1$. Thus $$ F^{-1}(U)sim F$$
with $Usim Unif(0,1)$. This method is called inverse transform.If $N>1$. Let $$ X=(X_1,X_2,dots,X_N)sim F $$
where $$F(x_1,dots,x_N)=mathbb{P}(X_1le x_1,dots, X_Nle x_N).$$
If $X_1,dots,X_N$ are independent, then $$F(x_1,dots,x_N)=mathbb{P}(X_1le x_1)cdots mathbb{P}(X_Nle x_N)=F_{X_1}(x_1)cdots F_{X_N}(x_N).$$
Thus is possible to simulate each $X_i$ by inverse transform method and so
$$ (F_{X_1}^{-1}(U_1),dots,F_{X_N}^{-1}(U_N))sim F$$
where $U_1,dots,U_N$ i.i.d. with $U_1sim Unif(0,1)$.
If $X_1,dots,X_N$ are dependent then a procedure that takes this into account is necessary.
So the sufficiency condition here is that $F$ is invertible?
– gigalord
yesterday
Yes, although this is a very strong hypothesis, and in practice difficult to achieve. Also, note that when $N = 1$ we use a generalized inverse, and even this method is not widely used in practice. In practice, Markov Chain Monte Carlo is used to simulate a complex distribution.
– Daniel Camarena Perez
yesterday
In the one-dimensional case the "probability integral transform" is used quite routinely. It's especially easy to implement in the discrete setting, where there are also alternatives that avoid the need for a binary search lookup (by using some preprocessing).
– Ian
yesterday
An example with dependence is a Markov chain columbia.edu/~ks20/4703-Sigman/4703-07-Notes-MC.pdf
– Daniel Camarena Perez
2 hours ago
add a comment |
up vote
1
down vote
accepted
up vote
1
down vote
accepted
If $N=1$ then it is always possible.
Let $$ Xsim F, $$
there exists $$F^{-1}(u)=inf {xin mathbb{R}colon F(x)ge u}$$ where $0< u<1$. Thus $$ F^{-1}(U)sim F$$
with $Usim Unif(0,1)$. This method is called inverse transform.If $N>1$. Let $$ X=(X_1,X_2,dots,X_N)sim F $$
where $$F(x_1,dots,x_N)=mathbb{P}(X_1le x_1,dots, X_Nle x_N).$$
If $X_1,dots,X_N$ are independent, then $$F(x_1,dots,x_N)=mathbb{P}(X_1le x_1)cdots mathbb{P}(X_Nle x_N)=F_{X_1}(x_1)cdots F_{X_N}(x_N).$$
Thus is possible to simulate each $X_i$ by inverse transform method and so
$$ (F_{X_1}^{-1}(U_1),dots,F_{X_N}^{-1}(U_N))sim F$$
where $U_1,dots,U_N$ i.i.d. with $U_1sim Unif(0,1)$.
If $X_1,dots,X_N$ are dependent then a procedure that takes this into account is necessary.
If $N=1$ then it is always possible.
Let $$ Xsim F, $$
there exists $$F^{-1}(u)=inf {xin mathbb{R}colon F(x)ge u}$$ where $0< u<1$. Thus $$ F^{-1}(U)sim F$$
with $Usim Unif(0,1)$. This method is called inverse transform.If $N>1$. Let $$ X=(X_1,X_2,dots,X_N)sim F $$
where $$F(x_1,dots,x_N)=mathbb{P}(X_1le x_1,dots, X_Nle x_N).$$
If $X_1,dots,X_N$ are independent, then $$F(x_1,dots,x_N)=mathbb{P}(X_1le x_1)cdots mathbb{P}(X_Nle x_N)=F_{X_1}(x_1)cdots F_{X_N}(x_N).$$
Thus is possible to simulate each $X_i$ by inverse transform method and so
$$ (F_{X_1}^{-1}(U_1),dots,F_{X_N}^{-1}(U_N))sim F$$
where $U_1,dots,U_N$ i.i.d. with $U_1sim Unif(0,1)$.
If $X_1,dots,X_N$ are dependent then a procedure that takes this into account is necessary.
edited yesterday
answered 2 days ago
Daniel Camarena Perez
56228
56228
So the sufficiency condition here is that $F$ is invertible?
– gigalord
yesterday
Yes, although this is a very strong hypothesis, and in practice difficult to achieve. Also, note that when $N = 1$ we use a generalized inverse, and even this method is not widely used in practice. In practice, Markov Chain Monte Carlo is used to simulate a complex distribution.
– Daniel Camarena Perez
yesterday
In the one-dimensional case the "probability integral transform" is used quite routinely. It's especially easy to implement in the discrete setting, where there are also alternatives that avoid the need for a binary search lookup (by using some preprocessing).
– Ian
yesterday
An example with dependence is a Markov chain columbia.edu/~ks20/4703-Sigman/4703-07-Notes-MC.pdf
– Daniel Camarena Perez
2 hours ago
add a comment |
So the sufficiency condition here is that $F$ is invertible?
– gigalord
yesterday
Yes, although this is a very strong hypothesis, and in practice difficult to achieve. Also, note that when $N = 1$ we use a generalized inverse, and even this method is not widely used in practice. In practice, Markov Chain Monte Carlo is used to simulate a complex distribution.
– Daniel Camarena Perez
yesterday
In the one-dimensional case the "probability integral transform" is used quite routinely. It's especially easy to implement in the discrete setting, where there are also alternatives that avoid the need for a binary search lookup (by using some preprocessing).
– Ian
yesterday
An example with dependence is a Markov chain columbia.edu/~ks20/4703-Sigman/4703-07-Notes-MC.pdf
– Daniel Camarena Perez
2 hours ago
So the sufficiency condition here is that $F$ is invertible?
– gigalord
yesterday
So the sufficiency condition here is that $F$ is invertible?
– gigalord
yesterday
Yes, although this is a very strong hypothesis, and in practice difficult to achieve. Also, note that when $N = 1$ we use a generalized inverse, and even this method is not widely used in practice. In practice, Markov Chain Monte Carlo is used to simulate a complex distribution.
– Daniel Camarena Perez
yesterday
Yes, although this is a very strong hypothesis, and in practice difficult to achieve. Also, note that when $N = 1$ we use a generalized inverse, and even this method is not widely used in practice. In practice, Markov Chain Monte Carlo is used to simulate a complex distribution.
– Daniel Camarena Perez
yesterday
In the one-dimensional case the "probability integral transform" is used quite routinely. It's especially easy to implement in the discrete setting, where there are also alternatives that avoid the need for a binary search lookup (by using some preprocessing).
– Ian
yesterday
In the one-dimensional case the "probability integral transform" is used quite routinely. It's especially easy to implement in the discrete setting, where there are also alternatives that avoid the need for a binary search lookup (by using some preprocessing).
– Ian
yesterday
An example with dependence is a Markov chain columbia.edu/~ks20/4703-Sigman/4703-07-Notes-MC.pdf
– Daniel Camarena Perez
2 hours ago
An example with dependence is a Markov chain columbia.edu/~ks20/4703-Sigman/4703-07-Notes-MC.pdf
– Daniel Camarena Perez
2 hours ago
add a comment |
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