# Search results

1. ### Need statistical test for contingency table with very small and big counts

Thanks for the reply. I was hoping I could have the null hypothesis set up such that I would be rejecting the null-hypothesis of dependence. This should permit me to know when there is evidence to suggest that the two variables are dependent, right? If that is the case, then my earlier comment...
2. ### Need statistical test for contingency table with very small and big counts

I have a 2x2 contingency table, and I want to discover how likely it is that the two events are dependent. The top-left cell is usually in the range of 1-10. The bottom-right cell can be over 3 billion. The other two cells are in the hundreds or millions (exclusively). I have tried Pearson's...
3. ### Using Simulation for Graph Visualization

I have been thinking about this for quite a while, and thought of the following simulation: for node in graph: node.x = <arbitrary value near 0> must be distinct per row node.velocity = 0 for number of STEPS: for node in graph: node.accel = 0 for node's row...
4. ### Using Simulation for Graph Visualization

Firstly, let me excuse myself for not knowing the most appropriate location to post this question. This is a question pertaining to Graph Theory, but the heart of the application is intended to be driven by the math and/or simulation of classical physics. At work I am currently attempting to...
5. ### Coefficients in expansion of product(1-x^a, a=1n)?

I stumbled across an interesting connection between partitioning n into k parts from any finite subset of the natural numbers and the partition functions p(n) and q(n). To be precise, if n,k are non-negative integers, S \subset \mathbb{N}, and S has a maximum: Let p_{S-k}(n) be the number of...
6. ### Coefficients in expansion of product(1-x^a, a=1n)?

I just found an excellent resource. http://functions.wolfram.com/IntegerFunctions/PartitionsQ/introductions/Partitions/ShowAll.html It covers both of the functions you mentioned, p(n) (unordered partitions of n with repetition) and q(n) (unordered partitions of n without repetition) concisely...
7. ### Coefficients in expansion of product(1-x^a, a=1n)?

That observation is related to the problem I was trying to solve! I realize now that a subproblem of what I'm doing is counting the number of ways to partition a natural number into any number of unordered positive parts. This equation was a piece of the resulting generating function (the part I...
8. ### Coefficients in expansion of product(1-x^a, a=1n)?

I have an equation of the form (1-x)(1-x^2)(1-x^3)\cdot\cdot\cdot(1-x^n). Or, in maple notation, product(1-x^a, a=1..n). I've been trying to find a way to express this as an expanded polynomial in sigma notation so that I can extract coefficients (for an enumerative generating function). If the...
9. ### Loop-the-loop in roller coaster

If friction and air resistance are negligible, it's a whole 'nother question you're dealing with. The change in velocity would depend entirely in the change in graviational potential energy (the vertical work done by gravity), otherwise energy is conserved and Ek is still the same. If Ek is...
10. ### Loop-the-loop in roller coaster

You would need more information, such as the loss of kinetic energy in the coaster, or the average force of friction.
11. ### Shining Light - The Physics Behind This Phenomenon?

That's one thing I wasn't clear on myself, and need to explain better once I understand it more. I don't think it's so much that it's bending it, but that the waves can go around obstacles. And that results in interference. Similar to the Double Slit Experiment. I think... Clarification, anyone?
12. ### Shining Light - The Physics Behind This Phenomenon?

I could not find an objective explanation of Diffraction Spikes anywhere... not even on Wikipedia. Most sites just referenced little things you could do, and the overall effect. I found a couple sites that explained very briefly what happens, so I tried to piece together all of these things to...
13. ### Shining Light - The Physics Behind This Phenomenon?

It seems like it'll be anything that obstructs light directly before entering the lens. You can even place strings in front of a telescope and get diffraction spikes (as russ_watters has apparently done).
14. ### Shining Light - The Physics Behind This Phenomenon?

Diffraction spikes, brilliant! Thanks. I get many excellent hits with this term. Thank-you.
15. ### Shining Light - The Physics Behind This Phenomenon?

It's always up with respect to the orientation of the camera. I took another picture to clarify: http://img142.imageshack.us/img142/9733/physicsphotorotatekn4.jpg [Broken] So I guess that means it has to do with the lens inside the camera. Is there anything specific I can research?
16. ### Shining Light - The Physics Behind This Phenomenon?

I've taken a picture of my christmas lights. I'm wondering if someone could help me explain, or at least name, the phenomenon? http://img142.imageshack.us/img142/5925/physicsphotocontestto9.jpg [Broken] Why does light appear to come from 4 distinct points around the light? Even though...
17. ### What If We Had Negative Mass?

Ah, I gotchya. I've taken note, and have lots more ideas for additions. :) Unfortunately I'm going to have to restrict the report now to kinematics and planetary motion. It's already getting really bulky. But I'll try to fit in more "what if" scenarios for the scale and such. Too bad I...
18. ### What If We Had Negative Mass?

Well what I said is that it measures the magnitude of the normal force. This is then internally proportioned to "weight" by the balance... It should be the same. I'm wondering why I'm being quizzed. Could someone begin to correct me? I'm sure I've made mistakes all over the place. ;)
19. ### What If We Had Negative Mass?

Well this is what I have for my current chart of how bodies of different masses affect eachother. For each negative object, the acceleration opposes the direction of the force of gravity, since Fnet = ma and m is negative. For each positive object, the acceleration is in the same...
20. ### What If We Had Negative Mass?

A negative mass and a positive mass would both exert repelling forces against eachother, correct? But the effect of a repulsive force on a negative mass still results in acceleration towards the positive body, because Fnet = ma, and m is negative, so acceleration is in the opposite direction...
21. ### What If We Had Negative Mass?

This isn't really a homework question... but it is homework... and I have a question... so I thought I might as well post it here. This is part of my grade 12 Physics curriculum. For our project, we're supposed to ask ourselves "What if <this happened>?" I chose to do mine on negative...

Hmm. Very cool. :smile:
23. ### PHP error

Are you able to except the error, and put some sort of default "feeds are temporarily unavailable at the moment" message?
24. ### C/++/# C++ homework

Okay. It was the "real number of six decimal digits" that threw me off. Thanks for the information D H.
25. ### Ajax Problem

Whatta, what I had just finished describing was client side. AJAX is client side. A request is client side. The client builds a request, with javascript, and sends this request to a server. That's AJAX.
26. ### Ajax Problem

No, I think whatta meant that since AJAX has to construct a request to the server manually, it's not encoding the request correctly. Make sure AJAX is correctly encoding it. In AJAX, you have to manually encode everything, or use an appropriate encode function. For example, in AJAX you have...
27. ### C/++/# C++ homework

Are you sure you aren't overcrediting your sources? I've got these facts from O'REILLY, which is a highly credible source for programming. Plus if you print out the constant FLT_DIG from float.h you get 6. #include <stdio.h> #include <float.h> int main( ) { float pi_1 =...
28. ### C/++/# C++ homework

Edit : You know you're too old... when? When you treat everything as it was back in the (good old) days, when we used C. I forgot we're talking about C++ standards here. Apolagies D H. Another thing that I didn't realise is that C will automatically round for you anyways. ISO 9899 and...
29. ### C/++/# C++ homework

There's no sense in being less accurate than you have to. :confused:
30. ### C/++/# C++ homework

I have one question and one "warning". Why does the user input values in inches, but then cost in \$/cm? Was that your choice, or might that be a mistake? Seems quite awkward. You define pi as 3.14159265, but on a standard compiler, float stores the first 6 digits. 3.14159265 will become...