Mathematica

Silly question on Matrices
Hello there I am new to Mathematica. In one of my attempts to understand how it works, I tried the following example A={{1,2,3},{4,5,6},{7,8,9}} //MatrixForm The result seems to be a matrix 3x3 but when I try A[[1][1]], the whole first line shows up instead of just one element. If I don't use MatrixForm, ... 5 Aug 2010 08:01

More streamline with StreamDensityPlot
Hi, Is there anyway to increase the streamline in StreamDensityPlot? The StreamPoints option seems to give only the maximum streamlines. Thanks in advances, Michuco ... 4 Aug 2010 05:59

Plotting a parametric equation
Greetings, I would like to see the graph of u=.5(x+y), v=.5(x-y), w= z - .5(x^2 - y^2). I entered this into the command-line of Mathematica: ParametricPlot3D[{0.5` (x + y), 0.5` (x - y), z - 0.5` (x^2 - y^2)}, {x, -1000000, 1000000}, {y, -1000000, 1000000}] All I get is a big empty box spanning from ... 4 Aug 2010 08:08

How to require integer subscripts to match a simple pattern
I am trying to create an indexed function that would be of the form M_(j,,j+1) [a,b] := func(j,a,b) , where M has the two subscripts j and j+1, i. e. I need the 2nd subscript to match only when it is 1 more than the first. I know how to do this if I made the argument 'j' a normal argument, that is, not a sub... 4 Aug 2010 08:08

Relationship between vertices and indices with GraphDistanceMatrix
Jon Harrop wrote: Given a graph represented as edges between vertices, such as the following: g = {"1" -> "2", "1" -> "10", "1" -> "11", "2" -> "3", "2" -> "18", "3" -> "4", "3" -> "12", "4" -> "5", "4" -> "19", "5" -> "6", "5" -> "13", "6" -> "7", "6" -> "20", "7" -> "8", "7" -> "14", "8" -> "... 7 Aug 2010 01:49

AbsoluteTime and Daylight Saving Time
The Mathematica documentation states that "AbsoluteTime[] uses whatever date and time have been set on your computer system. It performs no corrections for time zones, daylight saving time, etc." This statement confuses me. When I execute the following commands on my machine (Mathematica 7 running under Mac OS 10... 12 Aug 2010 06:01

Ignore my past two posts
They were about uniform distributions to create a point inside a tetrahedron. There is a much simpler way which I have already implemented. Sorry for possibly wasting anyone's time. Steve Gray ... 3 Aug 2010 07:03

Relationship between vertices and indices with GraphDistanceMatrix
Given a graph represented as edges between vertices, such as the following: g = {"1" -> "2", "1" -> "10", "1" -> "11", "2" -> "3", "2" -> "18", "3" -> "4", "3" -> "12", "4" -> "5", "4" -> "19", "5" -> "6", "5" -> "13", "6" -> "7", "6" -> "20", "7" -> "8", "7" -> "14", "8" -> "9", "8" -> "16", "9" -> "10", "... 3 Aug 2010 07:03

Simple Q
Dear All I have the expression E^(I km Subscript[X, 0] + I \[Lambda] Subscript[X, 0]) (-(1/2) I kz^2 Am[Subscript[X, 1]] Coss[(m \[Pi] y)/B] - 1/2 I km \[Lambda] Am[Subscript[X, 1]] Coss[(m \[Pi] y)/B]) + E^(I km Subscript[X, 0] - I \[Lambda] Subscript[X, 0]) (1/2 I kz^2 Am[Subscript[X, 1... 4 Aug 2010 08:08

export to file with a specific precision
Hello. I need to export to a file several numbers with a specific number of digits on the right of the decimal. I'm trying this with the function NumberForm[] and Export[] but the problem is that export function is not exporting only the number but the full inputform. For example, if I do this: Export["teste.... 4 Aug 2010 05:59