Posts by DavidB

Matlab keeps gving me error message that polymial is not uniquie when i use polyfit() command

THx

Does the data include multiple points for the same x-value? For example, (2, 3); (2, 10); (2, 7); . . . ? If so, you may have to analyze one branch of the data at a time; I don't know how else you'd create a fit for data containing multiple y-values for a given x-value.

I don’t have my MATLAB manual handy at the moment, but it sounds like you are trying to do something like a least squares fit (the approximating line does NOT have to pass through all the data points, but the overall difference should be a minimum). And you know ahead of time what kind of relationship the data has: linear, quadratic, cubic, etc. Is this correct?

There are several programs beside MATLAB that can do that for you. And source code is available. In addition, here is a Javascript utility that does Linear Least-Squares Data-Fitting:

http://www.akiti.ca/LinLeastSqPoly4.html

On the other hand, if you want to create points such that a smooth line can then be drawn that DOES pass through existing data points, Cubic Spline Interpolation might be more appropriate. Again, many other programs can do this, and there is much source code available. And here is another Javascript utility, one that does Cubic Spline Interpolation:

http://www.akiti.ca/CubicSpline.html

Regards,

David

Since your site is technical, you might also consider participating in a few relevant Usenet groups. There is also MSN and Yahoo! groups, but some of them are pretty quiet and I don't find them to be as cutting-edge as the Usenet groups.

I assume you have submitted your site to directories, specifically, forum directories.

Having a few links in del.icio.us helps too, as well as similar social bookmarking sites.

Do you have a blog? You might consider starting one. Make sure it includes links to your forum. Then submit the blog to blog listings with the appropriate tags--another base covered.

Regarding the forum itself: try to ensure all posts get a response. When I see a forum with a lot of posts without responses, I drift away.

Regards,

David

Nice list.

I didn't check out everything listed, however, I noticed Zeal is there. Zeal has been shut down.

Regards,

David

I am in need of finding the best keywords for my forum on google adwords, does anybody have any good sites/tools i should use?

Thanks in advance,

YoungCoder

If you are using Google Adwords, you are already using one of the best tools available (it should give you an idea what words are most sought, clicked-through, etc.). All other services offer very rough approximations.

From the other side, you could also consider creating an AdSense account and bidding for many of the keywords you are considering. After a few months (a year? etc. depends on your budget), you should have a very good idea what terms are most sought and clicked through.

Regards,

David

What are some good free directories that I can submit some of my sites to? I have all different categories of websites. Is there anything I should watch for when submitting to a free directory that would have a negative effect on my seo for these sites? None of these sites rank yet I am just trying to get them crawled for now but in the future is there anything I would want to watch out for? Thanks!

I don't think any directory can have a NEGATIVE effect on a site, but many of them could have a zero effect on your website (i.e. - they do not pass on PageRank and do nothing except waste your time).

You might check out the Info Vilesilencer website:

http://info.vilesilencer.com/

Dan does a good job of listing free, SEO-friendly, directories. You could go onto several webmastering forums (such as SP and DP), where directory owners present their new directories and solicit website submissions; however, Dan is usually on several of these forums himself, and updates his list about once a month. So you could save yourself the trouble of visiting a bunch of forums, and just keep an eye on the Info Vilesilencer website for updates.

A couple other features:
1) If you sign up for an update e-mail, Dan will send you an e-mail whenever the list has been updated (about once a month).
2) If you don’t want to wait for each month’s …

Hi, John.

Glad to see you here. I browse the SP forums occassionally, but have really not been active. After reading about directory submission, forums, article submission, SEO techniques, etc., reading the same questions (posted by people new to the field) gets kind of boring, so my visits to SP are down to one quick browse per day, if that.

Good introduction! Very thorough. One question (curiousity): Why did you pick the "stymiee" handle? Does it have any particular meaning?

Regards,

David

Iam going to write my exam on design and analysis of algorithms next month .till now i don't know any thing abt this subject can any body will help me by giving suggestions like books to be studied ,weblinks etc... please....

Algorithms are often discussed in the "Software Development" forums: sub-forums:
"Computer Science and Software Design" and
"Software Developers' Lounge".

However, I am not clear about exactly what you do not understand. An introductory course on algorithms should give you a good overview on the field of algorithms and software design. Without going into detail about a specific application (writing a linear algebra program, calculating eigenvalues, etc.), what more would you like to know?

Regards,

David

Hi sorry if this is in the wrong forum.

Are there any computer games programmers here? If so, how did you start getting into the field (i.e. what courses you took, etc.)

Thanks :)

Hmmmnn. . . .

No responses since June 30.

Scott, you may want to post this question at gamedev.net, cgsociety.org, or igda.org (check out the UK chapters too).

Regards,

David

hI THERE, i need some advice from the software geeks.If i need to get a fairly impressive hold over Algorithms,is it necessary to master calculus,theory of computation,discrete maths(as i've found them 2 be related 2 Algo analysis 2 some xtent?

If the algorithms you write are for discrete mathematics then, yes, you do need an excellent hold of calculus, theory of computation, linear algebra, etc.

For example, if you were to write a program that does the Fast-Fourier Transform, and you didn't know the math behind it, you could write a program that works, but doesn't take advantage of the previous steps (or symmetry).

Another example: if you were to write a root-finding routine, you might simply write code based on the bisection algorithm. It would work, but it would not be elegant or efficient. However, if you had a better grasp of calculus, you might prefer code based on the secant method or Newton-Raphson method.

Even Games Developers, who you might think wouldn't be too mathematically involved, require a good grasp of math, especially linear algebra. They are always manipulating matrices, vectors, etc. and they want the code to execute as fast as possible. They could write adequate code, but the results wouldn't be realistic, and games players want their video games to be as realistic as possible. So Games Developers are constantly trying to improve their code. And many of those improvements come through a mastery of math.

Regards,

David

I think that's becos it can't handle imaginary numbers. If you want it to, you have to write conditions for it.

I second that suggestion.
sqrt(X) cannot handle negative numbers, so you'll first have to check to see if X is negative. If it is, change it to a positive, and keep track of the fact that the radical was negative (with, say, a flag variable). Then follow through with the rest of the quadratic equation and make sure to note the imaginary component.

-- David

Hi, folks.

Just joined these forums. They look pretty busy and seem to cover a lot of ground so I thought it would be worthwhile to join and contribute where I can.

A little about me:

I am a self-taught hobbyist programmer. Never been paid to program, but am pretty good with C, C++, and Javascript. Have also worked on a few websites, so know some HTML, and XHTML. Have barely touched Java and PHP.

Regards,

David