Correlated Chance Constraint












1












$begingroup$


If we want to satisfy the following constraint with the probability of 1-$epsilon$:



$$
mathcal{P}(a leq x) ge 1 - epsilon
$$

where $x$ is the decision variable, $a$ is a random variable with a normal distribution $ N(mu,sigma^2)$, it is enough to have
$$
x geq mu + sigma Phi^{-1}(1-epsilon)
$$



My question is what we can say about the same problem in a higher dimension, for example 2, where $a_1$ and $a_2$ are correlated.



$$
mathcal{P}(a_1 leq x_1 , a_2 leq x_2 ) ge 1 - epsilon
$$










share|cite|improve this question











$endgroup$












  • $begingroup$
    1. where did $mu$ go? 2. can you apply a linear transformation to eliminte the correlation?
    $endgroup$
    – LinAlg
    Jan 29 at 21:29










  • $begingroup$
    @LinAlg $mu$ was missed, it is fixed now.
    $endgroup$
    – Mahraz
    Jan 29 at 22:06










  • $begingroup$
    This problem won't have a closed-form solution in dimension $dgeq2$, even in the uncorrelated case, I don't think. It can be evaluated numerically.
    $endgroup$
    – David M.
    Feb 2 at 14:52












  • $begingroup$
    @DavidM. in uncorrelated case, I think we can simply decouple the problems into several one dimension problem and solve them respectively.
    $endgroup$
    – Mahraz
    Feb 4 at 20:37










  • $begingroup$
    I think you would still end up with a product of CDFs, which I don't think you could invert analytically.
    $endgroup$
    – David M.
    Feb 4 at 20:45
















1












$begingroup$


If we want to satisfy the following constraint with the probability of 1-$epsilon$:



$$
mathcal{P}(a leq x) ge 1 - epsilon
$$

where $x$ is the decision variable, $a$ is a random variable with a normal distribution $ N(mu,sigma^2)$, it is enough to have
$$
x geq mu + sigma Phi^{-1}(1-epsilon)
$$



My question is what we can say about the same problem in a higher dimension, for example 2, where $a_1$ and $a_2$ are correlated.



$$
mathcal{P}(a_1 leq x_1 , a_2 leq x_2 ) ge 1 - epsilon
$$










share|cite|improve this question











$endgroup$












  • $begingroup$
    1. where did $mu$ go? 2. can you apply a linear transformation to eliminte the correlation?
    $endgroup$
    – LinAlg
    Jan 29 at 21:29










  • $begingroup$
    @LinAlg $mu$ was missed, it is fixed now.
    $endgroup$
    – Mahraz
    Jan 29 at 22:06










  • $begingroup$
    This problem won't have a closed-form solution in dimension $dgeq2$, even in the uncorrelated case, I don't think. It can be evaluated numerically.
    $endgroup$
    – David M.
    Feb 2 at 14:52












  • $begingroup$
    @DavidM. in uncorrelated case, I think we can simply decouple the problems into several one dimension problem and solve them respectively.
    $endgroup$
    – Mahraz
    Feb 4 at 20:37










  • $begingroup$
    I think you would still end up with a product of CDFs, which I don't think you could invert analytically.
    $endgroup$
    – David M.
    Feb 4 at 20:45














1












1








1





$begingroup$


If we want to satisfy the following constraint with the probability of 1-$epsilon$:



$$
mathcal{P}(a leq x) ge 1 - epsilon
$$

where $x$ is the decision variable, $a$ is a random variable with a normal distribution $ N(mu,sigma^2)$, it is enough to have
$$
x geq mu + sigma Phi^{-1}(1-epsilon)
$$



My question is what we can say about the same problem in a higher dimension, for example 2, where $a_1$ and $a_2$ are correlated.



$$
mathcal{P}(a_1 leq x_1 , a_2 leq x_2 ) ge 1 - epsilon
$$










share|cite|improve this question











$endgroup$




If we want to satisfy the following constraint with the probability of 1-$epsilon$:



$$
mathcal{P}(a leq x) ge 1 - epsilon
$$

where $x$ is the decision variable, $a$ is a random variable with a normal distribution $ N(mu,sigma^2)$, it is enough to have
$$
x geq mu + sigma Phi^{-1}(1-epsilon)
$$



My question is what we can say about the same problem in a higher dimension, for example 2, where $a_1$ and $a_2$ are correlated.



$$
mathcal{P}(a_1 leq x_1 , a_2 leq x_2 ) ge 1 - epsilon
$$







optimization correlation






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 29 at 22:05







Mahraz

















asked Jan 29 at 21:16









MahrazMahraz

103




103












  • $begingroup$
    1. where did $mu$ go? 2. can you apply a linear transformation to eliminte the correlation?
    $endgroup$
    – LinAlg
    Jan 29 at 21:29










  • $begingroup$
    @LinAlg $mu$ was missed, it is fixed now.
    $endgroup$
    – Mahraz
    Jan 29 at 22:06










  • $begingroup$
    This problem won't have a closed-form solution in dimension $dgeq2$, even in the uncorrelated case, I don't think. It can be evaluated numerically.
    $endgroup$
    – David M.
    Feb 2 at 14:52












  • $begingroup$
    @DavidM. in uncorrelated case, I think we can simply decouple the problems into several one dimension problem and solve them respectively.
    $endgroup$
    – Mahraz
    Feb 4 at 20:37










  • $begingroup$
    I think you would still end up with a product of CDFs, which I don't think you could invert analytically.
    $endgroup$
    – David M.
    Feb 4 at 20:45


















  • $begingroup$
    1. where did $mu$ go? 2. can you apply a linear transformation to eliminte the correlation?
    $endgroup$
    – LinAlg
    Jan 29 at 21:29










  • $begingroup$
    @LinAlg $mu$ was missed, it is fixed now.
    $endgroup$
    – Mahraz
    Jan 29 at 22:06










  • $begingroup$
    This problem won't have a closed-form solution in dimension $dgeq2$, even in the uncorrelated case, I don't think. It can be evaluated numerically.
    $endgroup$
    – David M.
    Feb 2 at 14:52












  • $begingroup$
    @DavidM. in uncorrelated case, I think we can simply decouple the problems into several one dimension problem and solve them respectively.
    $endgroup$
    – Mahraz
    Feb 4 at 20:37










  • $begingroup$
    I think you would still end up with a product of CDFs, which I don't think you could invert analytically.
    $endgroup$
    – David M.
    Feb 4 at 20:45
















$begingroup$
1. where did $mu$ go? 2. can you apply a linear transformation to eliminte the correlation?
$endgroup$
– LinAlg
Jan 29 at 21:29




$begingroup$
1. where did $mu$ go? 2. can you apply a linear transformation to eliminte the correlation?
$endgroup$
– LinAlg
Jan 29 at 21:29












$begingroup$
@LinAlg $mu$ was missed, it is fixed now.
$endgroup$
– Mahraz
Jan 29 at 22:06




$begingroup$
@LinAlg $mu$ was missed, it is fixed now.
$endgroup$
– Mahraz
Jan 29 at 22:06












$begingroup$
This problem won't have a closed-form solution in dimension $dgeq2$, even in the uncorrelated case, I don't think. It can be evaluated numerically.
$endgroup$
– David M.
Feb 2 at 14:52






$begingroup$
This problem won't have a closed-form solution in dimension $dgeq2$, even in the uncorrelated case, I don't think. It can be evaluated numerically.
$endgroup$
– David M.
Feb 2 at 14:52














$begingroup$
@DavidM. in uncorrelated case, I think we can simply decouple the problems into several one dimension problem and solve them respectively.
$endgroup$
– Mahraz
Feb 4 at 20:37




$begingroup$
@DavidM. in uncorrelated case, I think we can simply decouple the problems into several one dimension problem and solve them respectively.
$endgroup$
– Mahraz
Feb 4 at 20:37












$begingroup$
I think you would still end up with a product of CDFs, which I don't think you could invert analytically.
$endgroup$
– David M.
Feb 4 at 20:45




$begingroup$
I think you would still end up with a product of CDFs, which I don't think you could invert analytically.
$endgroup$
– David M.
Feb 4 at 20:45










1 Answer
1






active

oldest

votes


















0












$begingroup$

Partial answer (too long for comment). You can evaluate the bivariate normal CDF numerically (using e.g. Python and Scipy, which is what I did). We see that, even in the correlated case, the feasible region is convex, which is a hopeful sign, computationally (basically the CDF of the bivariate normal distribution is quasi-convex).



For these numerical examples, I took $mu_1=mu_2=0$, $sigma_1=0.2$, $sigma_2=0.4$ and covariance matrix
$$
Sigma=begin{bmatrix}
sigma_1^2 & rhosigma_1sigma_2\rhosigma_1sigma_2 & sigma_2^2
end{bmatrix}
$$

where $rhoin[0,1]$ is the correlation parameter. Here's $rho=0.5$, with $varepsilon=0.4$.



feasible region for rho=0.5



The simplest naive approximation to this region would be
$$
x_igeqmu_i+Phi^{-1}(1-varepsilon)sigma_i.
$$

In general, this approximation isn't great:
poor linear approximation



But, counter-intuitively (to me), this approximation seems to be exact in the limit $rhoto1$. Here's $rho=0.99$:
good linear approximation






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Thanks for your explanation.
    $endgroup$
    – Mahraz
    Feb 4 at 20:42












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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









0












$begingroup$

Partial answer (too long for comment). You can evaluate the bivariate normal CDF numerically (using e.g. Python and Scipy, which is what I did). We see that, even in the correlated case, the feasible region is convex, which is a hopeful sign, computationally (basically the CDF of the bivariate normal distribution is quasi-convex).



For these numerical examples, I took $mu_1=mu_2=0$, $sigma_1=0.2$, $sigma_2=0.4$ and covariance matrix
$$
Sigma=begin{bmatrix}
sigma_1^2 & rhosigma_1sigma_2\rhosigma_1sigma_2 & sigma_2^2
end{bmatrix}
$$

where $rhoin[0,1]$ is the correlation parameter. Here's $rho=0.5$, with $varepsilon=0.4$.



feasible region for rho=0.5



The simplest naive approximation to this region would be
$$
x_igeqmu_i+Phi^{-1}(1-varepsilon)sigma_i.
$$

In general, this approximation isn't great:
poor linear approximation



But, counter-intuitively (to me), this approximation seems to be exact in the limit $rhoto1$. Here's $rho=0.99$:
good linear approximation






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Thanks for your explanation.
    $endgroup$
    – Mahraz
    Feb 4 at 20:42
















0












$begingroup$

Partial answer (too long for comment). You can evaluate the bivariate normal CDF numerically (using e.g. Python and Scipy, which is what I did). We see that, even in the correlated case, the feasible region is convex, which is a hopeful sign, computationally (basically the CDF of the bivariate normal distribution is quasi-convex).



For these numerical examples, I took $mu_1=mu_2=0$, $sigma_1=0.2$, $sigma_2=0.4$ and covariance matrix
$$
Sigma=begin{bmatrix}
sigma_1^2 & rhosigma_1sigma_2\rhosigma_1sigma_2 & sigma_2^2
end{bmatrix}
$$

where $rhoin[0,1]$ is the correlation parameter. Here's $rho=0.5$, with $varepsilon=0.4$.



feasible region for rho=0.5



The simplest naive approximation to this region would be
$$
x_igeqmu_i+Phi^{-1}(1-varepsilon)sigma_i.
$$

In general, this approximation isn't great:
poor linear approximation



But, counter-intuitively (to me), this approximation seems to be exact in the limit $rhoto1$. Here's $rho=0.99$:
good linear approximation






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Thanks for your explanation.
    $endgroup$
    – Mahraz
    Feb 4 at 20:42














0












0








0





$begingroup$

Partial answer (too long for comment). You can evaluate the bivariate normal CDF numerically (using e.g. Python and Scipy, which is what I did). We see that, even in the correlated case, the feasible region is convex, which is a hopeful sign, computationally (basically the CDF of the bivariate normal distribution is quasi-convex).



For these numerical examples, I took $mu_1=mu_2=0$, $sigma_1=0.2$, $sigma_2=0.4$ and covariance matrix
$$
Sigma=begin{bmatrix}
sigma_1^2 & rhosigma_1sigma_2\rhosigma_1sigma_2 & sigma_2^2
end{bmatrix}
$$

where $rhoin[0,1]$ is the correlation parameter. Here's $rho=0.5$, with $varepsilon=0.4$.



feasible region for rho=0.5



The simplest naive approximation to this region would be
$$
x_igeqmu_i+Phi^{-1}(1-varepsilon)sigma_i.
$$

In general, this approximation isn't great:
poor linear approximation



But, counter-intuitively (to me), this approximation seems to be exact in the limit $rhoto1$. Here's $rho=0.99$:
good linear approximation






share|cite|improve this answer









$endgroup$



Partial answer (too long for comment). You can evaluate the bivariate normal CDF numerically (using e.g. Python and Scipy, which is what I did). We see that, even in the correlated case, the feasible region is convex, which is a hopeful sign, computationally (basically the CDF of the bivariate normal distribution is quasi-convex).



For these numerical examples, I took $mu_1=mu_2=0$, $sigma_1=0.2$, $sigma_2=0.4$ and covariance matrix
$$
Sigma=begin{bmatrix}
sigma_1^2 & rhosigma_1sigma_2\rhosigma_1sigma_2 & sigma_2^2
end{bmatrix}
$$

where $rhoin[0,1]$ is the correlation parameter. Here's $rho=0.5$, with $varepsilon=0.4$.



feasible region for rho=0.5



The simplest naive approximation to this region would be
$$
x_igeqmu_i+Phi^{-1}(1-varepsilon)sigma_i.
$$

In general, this approximation isn't great:
poor linear approximation



But, counter-intuitively (to me), this approximation seems to be exact in the limit $rhoto1$. Here's $rho=0.99$:
good linear approximation







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Feb 2 at 15:19









David M.David M.

2,188421




2,188421












  • $begingroup$
    Thanks for your explanation.
    $endgroup$
    – Mahraz
    Feb 4 at 20:42


















  • $begingroup$
    Thanks for your explanation.
    $endgroup$
    – Mahraz
    Feb 4 at 20:42
















$begingroup$
Thanks for your explanation.
$endgroup$
– Mahraz
Feb 4 at 20:42




$begingroup$
Thanks for your explanation.
$endgroup$
– Mahraz
Feb 4 at 20:42


















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