Questions tagged [weighted-least-squares]
This tag is for questions relating to weighted least squares, a generalization of ordinary least squares and linear regression in which the errors covariance matrix is allowed to be different from an identity matrix.
64 questions
1 vote
1 answer
94 views
Weighted least-squares that minimizes the operator norm
I have a question that is related to weighted least-squares and operator norm. Assume we have a model $y(x) = a_1 \psi_1 + \dots + a_n \psi_n(x)$ and its noisy $N (>n)$meaurements $$ \{ (x_1, y(x_1)...
0 votes
1 answer
288 views
Solving minimum 2-norm least squares problem with a metric
I am trying to solve a standard least-squares problem of the form: $x = \text{argmin}|Ax-b|^2$, where $A$ has a non-trivial null space. I want the minimum 2-norm solution with the norm $\|x\|^2 = x^T ...
0 votes
0 answers
47 views
Least squares rational approximation to $\arcsin x + \sqrt{1-x^2}$ in form $[3,1]$
I'm trying to generate a decent $[3,1]$ rational least squares polynomial approximation to $\arcsin(x)+\sqrt{1-x^2}$ and failing dismally :( The problem is that for this particular combination of $N,D$...
4 votes
1 answer
124 views
Right pseudo-inverse and Generalized Least Squares
The left pseudoinverse of $(A^TA)^{-1}A^T$ solves the problem of $\text{min} ||b-Ax||^2$. i.e. $x=(A^TA)^{-1}A^Tb$ is the solution to above problem. And there is a well-know property that if we add a ...
1 vote
2 answers
170 views
Weighted Least Squares versus ordinary least squares wiki page
If I have a $(X, Y)$ dataset and want to model $y = f(x, \beta)$. In that case for OLS, I would have $$e(x_i, \beta) = f(x_i, \beta) - y_i$$ Then obviously I would have $$SSE = \sum_{i}e(x_i, \beta)^2$...
1 vote
0 answers
84 views
Time Weighted Decay
I've been tasked to calculate/forecast the weighted exposure of a financial product. I work with bunker prices and we have access to bunker future prices everyday. They look similar to this in an ...
2 votes
0 answers
95 views
Weighted Least Square with infinite weights
I am considering a weighted least square problem with data $X \in \mathbb{R}^{n \times p}$, (diagonal) weight matrix $W \in \mathbb{R}^{n \times n}$ and responses $y \in \mathbb{R}^n$, i.e. finding $$\...
0 votes
0 answers
175 views
Linear regression for data points with given deviations?
I have a problem I fail to research properly, so I hope you may at least push me in the right direction (or maybe even provide me an answer right away?). I know how linear regression works, that it ...
0 votes
0 answers
44 views
Weighted Least squares with Multiple Unknowns and Iterations
I am currently working on a problem involving the minimization of the $\chi^2$ deviation between a model matrix ($C_{model}$) and a measured matrix ($C_{measured}$). by finding the best fit parameters ...
2 votes
0 answers
178 views
Noise Covariance Estimation for Linear Regression (Seemingly Unrelated Regressions)
Considering following linear model \begin{equation} y_t = X_t f_t + \varepsilon_t, \qquad t=1,\cdots, T \end{equation} where $y_t\in\Re^{300\times 1}$ and $X_t\in\Re^{300\times 60}$ are two given ...
0 votes
0 answers
137 views
MSE of WLS estimator with biased measurements
(also posted on CV, but I will try here too) I am trying to find out if what I am looking at is a known problem. I am considering the case of weighted least squares, and I am trying to find the ...
1 vote
1 answer
228 views
Asymptotic Normality of Weighted LSE (Theorem 3.17, Jun Shao)
I am trying to understand Jun Shao's proof of the asymptotic normality of weighted LSE in his book Mathematical Statistics. The theorem: Consider the model $X = Z\beta + \varepsilon$ with a full rank $...
0 votes
1 answer
230 views
Weighted least squares formula
I was studying the weighted least squares algorithm and came across this formula for calculating the weighted result in terms of the original. Here $x_{LS}$ is the solution for $D=I$ I can't figure ...
3 votes
0 answers
139 views
Best way to remove a local maxima from a piecewise linear function
Let $x_1,...x_K \geq 0$ and $f$ be the piecewise-linear function given by $f(k)=x_k$ for every $1 \leq k \leq K$. Denote by $m$ the number of modes (i.e. local maxima) of $f$. Let's associate with ...
2 votes
0 answers
114 views
Weighted least squares problem with a equal quadratic constraint
We need to solve the following least square problem $$\min_x (Y-Ax)^TW(Y-Ax)$$ $$s.t. x^TA^TAx=1$$ $$c^Tx=0$$ in a closed form, where $Y \in \mathbb{R}^{n\times 1}$, $A \in \mathbb{R}^{n\times n}$, $W ...