Mathematica

WorkingPrecision in ODE
Who has any idea why NDSolve[{u''[t] + 1/2 u'[t] + Sin[u[t]] == 3/2 Sin[2/3 t], u[0] == 0, u'[0] == 0}, u, {t, 0, 200}, WorkingPrecision -> precision, MaxSteps -> Infinity] works if precision=50 but not if precision=60 ? (Error test failure at t=0.012758...) (tested with Mathematica 7.0) Thanks in adv... 16 Oct 2009 07:28

WorkingPrecision and NDSolve
Why does this instruction properly work if precision =60 but not if precision=70 (Message : error test failure at t=0.01316... ) : NDSolve[{x''[t] + x'[t] + Sin[x[t]] == Sin[t/3], x[0] == 0, x'[0] == 0}, x, {t, 0, 10}, WorkingPrecision -> 70] ? Thanks in advance, A. Hautot ... 22 Oct 2009 23:03

Region borders in WorldPlot
I am using the WorldPlot package and CountryData to show the locations of cities. Sadly there doesn't seem to be a way of showing the Region (i.e. Kent, Sussex, etc. for England, or California, Utah etc. for the USA). Is there a polygon package for region borders? Seems like a must have to me. ... 15 Oct 2009 08:18

closing curly brace unrecognized
I have Mathematica 7.0.1 installed on a Mac running X.4.11. I've just run into the problem (again) that the closing curly brace isn't recognized. Trying to enter a vector, I write vR = {w Cos[k z], w Sin[k z], z} and on hitting Shft-Enter the left curly brace is highlighted and the message lines appear... 15 Oct 2009 08:18

Mathematica 7.01 and Mac OS 10.6 (Snow Leopard)
I have been experiencing rare but very irritating problems running Mathematica 7.01 under Mac OS 10.6 (Snow Leopard) on a MacBook. What happens is that for some reason the kernel suddenly quits during an evaluation. When I try to restart it (by evaluating some expression) I get the message: "The kernel fail... 16 Oct 2009 07:28

trading
Who is using Mathematica for trading and backtesting? I just bought my copy and would like to model futures and options trading systems. Thanks, Joel --- http://twitter.com/wagerlabs ... 15 Oct 2009 08:18

Import from web addresses fails
The addresses are correct and the files are there, I can click on the addresses and down load the files... but all the Imports fail. Is this a problem with my Mathematica install? spotPrices=First(a)Import["http://www.eia.doe.gov/emeu/international/Crude1.xls"]; Import::nffil: File not found during Import. >> ... 12 Nov 2009 06:11

Piecewise vs. /; ?
I'm defining a piecewise function: mmin = 0.08; mmax = 100; \[Xi][m_] := Piecewise[ {{0.035 m^-1.3, 0.08 <= m <= 0.50}, {0.019 m^-2.2, 0.50 < m <= 1.00}, {0.019 m^-2.7, 1.00 < m <= 100}}]; (* stars per pc^3 *) This works fine for plotting (which I won't show) and integrating: In[5]:= Integ... 18 Oct 2009 06:15

undocumented feature: TableView
Hello, today I typed by accident "TableView" instead of "TableForm" writing a notebook, so I discovered a function apparently not documented in Mathematica 7 / Mac version. "TableView" displays a list in a spreadsheet-like format. I tried to search the DocumentationCenter without finding any information... 12 Oct 2009 07:22

Google Trends Data and Mathematica
I am looking for some advice for directly importing data from Google Trends? I am able to download the CSV files from Google and then load into Mathematica easily enough, but I would rather skip the intermediate steps and directly pull the data from Google into my Mathematica notebook. I think where I am getting st... 11 Oct 2009 18:13