"KH " <firstname.lastname@example.org> wrote in message <email@example.com>...
> I want to find out the first derivative of Dirac delta function. I got the answer from the symbolic toolbox and then converted it into a function handle.
> syms x
> a = matlabFunction(diff(dirac(x-10)));
> Matlab returns
> a =
> The answer is fine. Then, let's say if you evaluate a(10), the error says too many input arguments.
> Error in ==> sym.matlabFunction>makeFhandle/@(x)dirac(x-10,1)
> Can anyone tell me if it is an inherent error to evaluate the derivative of Dirac delta function in Matlab?
- - - - - - - - - - -
The Dirac delta function only becomes significant for non-Riemann type integrals where single points are allowed to have finite non-zero measure. If you say dirac(0) it will give inf as the answer but that does not reveal its true meaning. You could not put that value into an ordinary numerical integration and get a correct answer.
In the case of the derivative of the dirac function, it would have to have the property that some kind of double integration of it would give a finite answer at the value x = 0. You cannot expect anything reasonable to come of trying to evaluate such a derivative at the point 0. If it were to issue an inf value, that would be very short of the reality.
The error message you received is probably due to the symbolic toolbox creators never having expected anyone to make such a weird request. If they were to anticipate it, the message could well read something like this: "Never do that again!"
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.
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