Mathematica

how to extract coefficients of non-cosine term?
Hi guys, I expanded an expression which end up with a lot cosine term, such as Cos[w t],Cos[2w t], Cos[3w t].... My question is how to extract coefficient for non-cosine terms? I did my research with Google but couldn't find a solution. Thanks a lot! ... 8 Mar 2010 07:28

Mathematica function to calculate correlation coefficient?
Hi everyone, I solved a differential equation, and got a solution n(t). Now I have collected 8 data points at 8 different times. I plotted the solution of n(t), and the curve intersect the 8 data points quite well on a graph of n(t) vs. t. How do I use Mathematica 7.0 to calculate the correlation coefficien... 10 Mar 2010 01:57

Help Improving this integral calculation / solution
I have an integral I need to calculate, with one variable left symbolic, and then use the result to find a numerical solution to an equation, and the result of the integration is not giving me what I need: ------ d = .7; v = .05; a = .1; nk = (a + (1 - a) k v t)/(d + a + (1 - a) k v t); pg[k_] = Exp[1-k]; g... 9 Mar 2010 06:43

LaplaceTransform for integrodifferential equation with unit step
Hello Group, I can solve the following integro-differential equation using LaplaceTransform.(This one doesn't have unit step) In[17]:= LaplaceTransform[10 i[t] + 0.01 i'[t] + 1600\!\( \*SubsuperscriptBox[\(\[Integral]\), \(0\), \(t\)]\(i[z] \ [DifferentialD]z\)\) ==5, t, s] %//Expand %/. LaplaceTransfor... 5 Mar 2010 05:02

Scientific Astronomer and Simulating Sunlight
Anyone reading this group have a copy of Scientific Astronomer? I would like to purchase a copy to run the notebook Simulating Sunlight, which I found on the Wolfram site. Howard Fink ... 5 Mar 2010 05:02

EXPORT TO DIFFERENT FOLDERS
Hello all I am currently exporting different files to the folder set by SetDirectory["..."]. I have a loop that produces 5 files at a time and then start again and produce 5 other files. How could I ask the program to put each of these 5 files in a specific folder I created in the main folder ; the one set by SetDir... 15 Mar 2010 06:47

Possible bug? Changing fonts of greek letters
Hi I think I found a bug. Take a look at Plot[Sinc[x], {x, 0, 10}, AxesLabel -> {Style[\[Omega], FontFamily -> "Times"], x}, AxesStyle -> Directive[FontFamily -> "Times", Black, 40] ] Setting the font of \[Omega] to Times, Sylfaen, Helvetica, etc..., doesn't change its font. It stays the same. I'm runni... 7 Mar 2010 04:11

Alternatives to ARPACK?
Hi guys My system is currently described by a dense 2500x2500 matrix, which contains many zero entries. Diagonalizing this matrix using Eigensystem takes about 2 minutes, which seems like a long time, and I assume it has got something to do with the fact that the eigenvalues are degenerate. In order to investiga... 14 Mar 2010 07:36

clearing denominators and eliminating square roots in *huge*
Hello Community of Mathematica Users, My collaborators and I are having a nasty problem that I'm hoping you might be able to help us move beyond: After spending quite a few hours Solve[]-ing an equation, Mathematica returns an extremely large solution where all the terms contain complicated denominators and ... 5 Mar 2010 05:02

Communication over Mathlink with C/C++
O List, here is my plea for help Could somebody from Wolfram please have a complete and better example in the examples folder for C/C++ communication for the next release? And they can blog about it today on the Wolfram blog! addtwo/factor/quotient etc are so simple yet not completely practical. I will use addtw... 4 Mar 2010 05:34