Trying to understand least squares estimates

In summary, the conversation discusses the use of least squares to obtain the best solutions for systems like Ax=b, where b is not in the column space of A. It also mentions finding the values of x that minimize the L^2 distance ||Ax -b ||_2, which is the orthogonal projection of b onto Ax. The conversation concludes with the confirmation that the person is looking for the matrix multiplication.
  • #1
Nastya
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Hi, I'm trying to understand which mathematical actions I need to perform to be able to arrive at the solution shown in the uploaded picture. Thank you.
 

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  • #3
As a general statement, least squares allows you to obtain " best possible solutions " to systems like :

Ax=b , where b is not in the column space of A. This statement leads to a system like the one you attached to your post. You find the values of x that minimize the
## L^2 ## distance ## ||Ax -b ||_2 ##, and this is the orthogonal projection of b onto Ax.
 
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Likes Nastya
  • #4
mfb said:
Are you just looking for the matrix multiplication? If not, I don't understand what you are asking.
Yes, thank you. I will review the matrix multiplication.
 

1. What is the purpose of least squares estimates?

The purpose of least squares estimates is to find the line of best fit for a set of data points. It minimizes the sum of the squared distances between the data points and the line, providing a measure of how closely the line fits the data.

2. How is the least squares method used to estimate parameters?

The least squares method is used to estimate parameters by minimizing the sum of the squared errors between the actual data points and the predicted values from a mathematical model. The parameters are adjusted until the sum of the squared errors is at its minimum, providing the best fit for the data.

3. What is the difference between simple and multiple linear regression?

Simple linear regression involves one independent variable and one dependent variable, while multiple linear regression involves multiple independent variables and one dependent variable. The least squares method can be used for both types of regression to estimate the parameters of the model.

4. How does the least squares method deal with outliers?

The least squares method is sensitive to outliers, as they can significantly affect the position of the line of best fit. One way to deal with outliers is to use robust regression methods that are less affected by extreme values. Another approach is to remove the outliers from the dataset before running the least squares method.

5. Can the least squares method be used for non-linear relationships?

No, the least squares method is only suitable for linear relationships between variables. For non-linear relationships, other methods such as polynomial regression or non-linear least squares must be used to estimate the parameters.

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