I have searched through the Matlab forums, but haven't found the answer to my question. I would like to use a least squares function to fit some data.
Briefly, I have two equations of the form
Z1 = a + b*x + c*y + d*x*y
Z2 = e + f*x + g*y + h*x*y
where i know Z1, Z2, x, and y and they're in vector form. I have a few hundred data points, so the lack of data is not an issue. Is there a way I can use the lsqcurvefit function to figure out a thru h or is this a more complex problem?
"Samuel " <firstname.lastname@example.org> wrote in message <email@example.com>...
> Hi All,
> I have searched through the Matlab forums, but haven't found the answer to my question. I would like to use a least squares function to fit some data.
> Briefly, I have two equations of the form
> Z1 = a + b*x + c*y + d*x*y
> Z2 = e + f*x + g*y + h*x*y
> where i know Z1, Z2, x, and y and they're in vector form. I have a few hundred data points, so the lack of data is not an issue. Is there a way I can use the lsqcurvefit function to figure out a thru h or is this a more complex problem?
- - - - - - - - -
It depends on what your criterion for fitting is. You say you know the values for Z1, Z2, x, and y for a number of points and you used the phrase "least squares".
If you want to simply minimize the mean squares of the differences in the left and right hand sides of these equations, then you have an ordinary problem in linear least squares in determining the best values of the coefficients, a, b, c, ..., h, since the problem is linear in these coefficients.
On the other hand each of the equations represents a hyperbolic paraboloid surface in x, y, z space for a fixed set of coefficients and perhaps you wish to adjust these coefficients so that the mean square orthogonal distances from your points to the surface are at a minimum. That is a much more difficult problem, since it involves working with roots of sixth degree polynomials.
Just what sort of minimization do you have in mind? At this point it looks as though the two equations represent two entirely independent problems. Is there some connection between them that you haven't told us about, besides the fact that they have x and y values in common?
You can think of your watch list as threads that you have bookmarked.
You can add tags, authors, threads, and even search results to your watch list. This way you can easily keep track of topics that you're interested in. To view your watch list, click on the "My Newsreader" link.
To add items to your watch list, click the "add to watch list" link at the bottom of any page.
How do I add an item to my watch list?
To add search criteria to your watch list, search for the desired term in the search box. Click on the "Add this search to my watch list" link on the search results page.
You can also add a tag to your watch list by searching for the tag with the directive "tag:tag_name" where tag_name is the name of the tag you would like to watch.
To add an author to your watch list, go to the author's profile page and click on the "Add this author to my watch list" link at the top of the page. You can also add an author to your watch list by going to a thread that the author has posted to and clicking on the "Add this author to my watch list" link. You will be notified whenever the author makes a post.
To add a thread to your watch list, go to the thread page and click the "Add this thread to my watch list" link at the top of the page.
Tags for this Thread
No tags are associated with this thread.
What are tags?
A tag is like a keyword or category label associated with each thread. Tags make it easier for you to find threads of interest.
Anyone can tag a thread. Tags are public and visible to everyone.
About Newsgroups, Newsreaders, and MATLAB Central
What are newsgroups?
The newsgroups are a worldwide forum that is open to everyone. Newsgroups are used to discuss a huge range of topics, make announcements, and trade files.
Discussions are threaded, or grouped in a way that allows you to read a posted message and all of its replies in chronological order. This makes it easy to follow the thread of the conversation, and to see what’s already been said before you post your own reply or make a new posting.
Newsgroup content is distributed by servers hosted by various organizations on the Internet. Messages are exchanged and managed using open-standard protocols. No single entity “owns” the newsgroups.
There are thousands of newsgroups, each addressing a single topic or area of interest. The MATLAB Central Newsreader posts and displays messages in the comp.soft-sys.matlab newsgroup.
How do I read or post to the newsgroups?
You can use the integrated newsreader at the MATLAB Central website to read and post messages in this newsgroup. MATLAB Central is hosted by MathWorks.
Messages posted through the MATLAB Central Newsreader are seen by everyone using the newsgroups, regardless of how they access the newsgroups. There are several advantages to using MATLAB Central.
Your MATLAB Central account is tied to your MathWorks Account for easy access.
Use the Email Address of Your Choice
The MATLAB Central Newsreader allows you to define an alternative email address as your posting address, avoiding clutter in your primary mailbox and reducing spam.
Most newsgroup spam is filtered out by the MATLAB Central Newsreader.
Messages can be tagged with a relevant label by any signed-in user. Tags can be used as keywords to find particular files of interest, or as a way to categorize your bookmarked postings. You may choose to allow others to view your tags, and you can view or search others’ tags as well as those of the community at large. Tagging provides a way to see both the big trends and the smaller, more obscure ideas and applications.
Setting up watch lists allows you to be notified of updates made to postings selected by author, thread, or any search variable. Your watch list notifications can be sent by email (daily digest or immediate), displayed in My Newsreader, or sent via RSS feed.
Other ways to access the newsgroups
Use a newsreader through your school, employer, or internet service provider
Pay for newsgroup access from a commercial provider
Use Google Groups
Mathforum.org provides a newsreader with access to the comp.soft sys.matlab newsgroup