Mathematica

Strange slow performance on macbook pro
Hi, On Mathematica 7.0.1 I've noticed several strange behaviours regarding to time of calculations. I have MBP 2,56 4GB RAM (late 2009 model). I compared some notebooks with my friend computers (4 cores amd similar cpu freq) that is 2x faster than mine, however: -matrix multiplication is over 6 times slower on my... 7 Aug 2010 01:49

Rearrange equation II
I probably didn't explain properly: I've got a function G(x), which is: -(Sqrt[\[Pi]/2]*Erfc[x]*(-\[Mu]+Log[x]))/(2*Sqrt[\[Pi]]*\[Sigma]) The parameters mu and sigma are unknown. I would like to convert the formula so it has the Form: x=..... (So I kind of want to inverse the function). Is there a way to do so, wi... 8 Aug 2010 07:59

Convex hull in 3D
I'm pretty sure that a few years ago I downloaded a function that Eric W. wrote to compute the CH of some points in 3D. He intended it to be a temporary solution because Mathematica has CH only for 2D. I can't find it now and I need it. I have only a dozen or so random points and don't need super speed. Stev... 11 Aug 2010 04:55

Nonlinear fitting question
Hello Group, In the example below I want to do a fitting "exploiting" the correlation between y1 and y2 rather than separate them like I did. Like a 2D fitting thing. Also, in NonlinearModelFit, I dont like treating 1/(1+b) like another parameter. how to do it? best regards, Eric (* my model *) b = 1... 7 Aug 2010 01:49

Random points in triangle
I was looking for a simple way to place random points inside a triangle with uniform distribution. Here's a good way: newtri := Module[{x}, ptri = RandomReal[{-5, +5}, {3, 2}]; tredg = Subsets[ptri, {2}]; ] newpts[nump_] := Module[{wts}, inpoints = {}; Do [ wts = RandomReal[GammaDistribut... 12 Aug 2010 06:01

ListPlot with PlotStyle->Dashed causes problems
Mathematica 7.0.1.0 on Linux x86-64 (and x86-32) struggles when trying to plot the following data: ListPlot[{{0.5, -854.452}, {0.75, 95.8769}, {1., 100632.}, {1.25, 160.136}, {1.5, 132.}, {1.75, 109.569}, {2., 65.0497}, {2.25, 48.0858}, {2.5, 21.4803}, {2.75, 22.9186}, {3., 15.3401}, {3.25, 11.818}, {3.... 7 Aug 2010 01:49

automatically include automatic numbering in a
At this point I'm not asking for anything that fancy. My primary request is a way to create a cell style that automatically inserts the automatic numbering option. And a secondary request is to include automatically some boiler-plate within the cell when it is created. This is not to deny the utility of a h... 6 Aug 2010 07:09

BinLists in Array
Hello All I Would like to split this array: l={{1, 0}, {1, 1}, {1, 2}, {2, 3}, {2, 4}}, by the second element of each group, to group what are between 0-2, 2-4,4-6 and so on (just the second element) Using BinLists look like a good idea. I get my desirable result with: BinLists[{{1, 0}, {1, 1}, {1,... 7 Aug 2010 07:10

Suggestions
This was posted in 2003: "Selwyn Hollis" <selwynh(a)earthlink.net> wrote in message news:bgcupq$9qi$1(a)smc.vnet.net... Print preview should certainly be near the top of any wish list. (But if you're fortunate enough to have a Mac w/OS X, printing to PDF is almost as good.) To any such wis... 11 Aug 2010 04:55

Rearrange equation
I want to rearrange the equation below so that it would look like: x-> .... I tried: Solve[G==-(Sqrt[\[Pi]/2]*Erfc[x]*(-\[Mu]+Log[x]))/(2*Sqrt[\[Pi]]*\[Sigma]),x] But then I got the error message: Solve::tdep: The equations appear to involve the variables to be solved for in an essentially non-algebraic way. Is ... 6 Aug 2010 07:09