How to specify a specific constant for a multiple linear regression?

1 次查看（过去 30 天）
Khaled Ahmat
Khaled Ahmat 2017-10-14
回答： Khaled Ahmat 2017-10-17
I would like to know if it is possible to specify a certain constant to a multiple linear regression abd how?
  2 个评论
Khaled Ahmat
Khaled Ahmat 2017-10-14
I have a multiple linear regression using three predictor variables, say x1,x2,x3 the resulting equation is y=43-1.4x1+3.8x2-1.1x3 due to some presentation reasons I want to force the constant to be 30 instead of 43; so that the resulting equation becomes y=30-ax1+bx2-cx3;
is this possible in MATLAB?

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Image Analyst
Image Analyst 2017-10-14
See John's answer. https://www.mathworks.com/matlabcentral/answers/274980-linear-fit-to-data-with-intercept-at-origin#answer_214651
You can fit y-43 instead of y, then do the fit and add back in the 43 to get yFitted .
  4 个评论
显示 2更早的评论
Jan
Jan 2017-10-15
@Khaled Ahmat: Please use flags only to inform editors and admins about contributions, which might conflict with the terms of use e.g. by rudeness. Thanks.

请先登录，再进行评论。

更多回答（4 个）

Khaled Ahmat
Khaled Ahmat 2017-10-15
Thank you very much for your suggestion; my next question is how to run a Multiple linear regression without a constant in MATLAB? Is it the same function Regress(y,x) or there is another function for regression without a constant? Thank you in advance
  3 个评论
显示 1更早的评论
Khaled Ahmat
Khaled Ahmat 2017-10-15
编辑：Khaled Ahmat 2017-10-15
Yes it is a Multiple linear regression, but my question is how to make it with a zero constant in MATLAB
Image Analyst
Image Analyst 2017-10-15
But we already solved that in the first answer. If you don't know how to do it, then just attach vectors x1, x2, x3, and y in a .mat file.

请先登录，再进行评论。

Khaled Ahmat
Khaled Ahmat 2017-10-15
The m.file along with the data file is attached. Thank you for your effort
  2 个评论
Image Analyst
Image Analyst 2017-10-16
Not familiar with regress(). Why didn't you use the method of John D'Errico?
Khaled Ahmat
Khaled Ahmat 2017-10-16
编辑：Khaled Ahmat 2017-10-16
Actually I liked the method he which proposed y-30= ax1+bx2+cx3; and I am sure that there is a function in MATLAB for linear regression without a constant but now I am not able to get the function in MATLAB! This my Challenge now. If Mr John D'Errico can give us a clue about the function or an example it would be great

请先登录，再进行评论。

Image Analyst
Image Analyst 2017-10-17
I'm not sure I've got the columns correct for x1, x2, x3, and y, but this is essentially how you'd do it (again, thanks to John D'Errico):
% Read in data file.
data = importdata('Data_case1.txt')
% Extract columns into separate variables.
% Make sure the column numbers are the correct ones!!!!
x1 = data(:, 1);
x2 = data(:, 2);
x3 = data(:, 3);
y = data(:, 4);
% Construct x matrix
x = [x1, x2, x3];
% Construct y
y = y - 30;
% Get the cofficients:
coefficients = x \ y; % Estimate Parameter: x*coefficients = y
% Get fitted values for y. Be sure to add back in the 30 we subtracted!
y_estimated = x*coefficients + 30;
% Print them out
fprintf(' x1 x2 x3 y y_estimated\n');
for row = 1 : length(x1)
fprintf('%8.4f, %8.4f, %8.4f, %8.4f, %8.4f\n', ...
x1(row), x2(row), x3(row), y(row), y_estimated(row));
end
Khaled Ahmat
Khaled Ahmat 2017-10-17
It worked, thank you very much! Really appreciate it.

类别

在 Help Center 和 File Exchange 中查找有关 Linear and Nonlinear Regression 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by