Mathematica

Assumptions, Abs, etc.
Can anyone tell me why the following results appear? Clear[xc1, xc2] Simplify[Abs[xc1 - xc2]^2, Assumptions -> {xc1 < 0, xc2 < 0}] Simplify[Abs[xc1 - xc2]^2, Assumptions -> {xc1 < 0, xc2 > 0}] Simplify[Abs[xc1 - xc2]^2, Assumptions -> {xc1 > 0, xc2 < 0}] Simplify[Abs[xc1 - xc2]^2, Assumptions -> {xc1 > 0, xc2 > ... 7 Jun 2010 08:31

PlotMarkers and DateListPlot
Hi all, I'm trying to use some Graphics elements as markers for data points in my DateListPlot. I'm running into an issue where the first element of the PlotMarker list is being superimposed on every point in the plot. Here is the code which returns similarly undesired behavior. Instead of letters, I'm using poi... 7 Jun 2010 08:31

Push to clipboard?
Dear Group, is there any programmatical way to push an expression to the clipboard? I would like to have a button which sends a variable to the clipboard without opening a new notebook, or without selecting anything, much like this hypothetical code would do: var = "this text has been copied" Button["Copy to ... 11 Jun 2010 02:42

Simplifying complicated expressions
Suppose I have a long complex expression in which terms like (x^2+y^3-x^2y^2+Sqrt[z3+y2]) (for a simple example) appear many times along with various powers and the reciprocals of it, etc. To make the expression comprehensible and to make the computation faster, I would like to substitute say "f1xyz" for it eve... 19 Jun 2010 08:00

Mac OS X hard disk space used up by virtual memory
I've had another go at tackling this, again with no luck. All the arrays are being overwritten (i.e. with names = Names["@"];namedmemtot = Total[Table[ByteCount[Symbol[names[[i]]]], {i, Length[names]}]]; namedmemtot does not increase with each gif being processed. Nor does LeafCount increase), but somehow the memory ... 4 Jun 2010 09:12

discretized Laplacian or linear inverse problem with extremely
On Jun 3, 4:47 am, Igor <i.e.koz...(a)gmail.com> wrote: Hello! There are: A n*n matrix x n*1 matrix==column b n*1 matrix==column and the well known equation A.x==b I know columns x and b I want Mathematica to derive matrix A Of course, generally, this is a complicated problem, but ... 4 Jun 2010 08:06

DSolve bug in 7.0.0
Dear All, the following call gives different results under different Mathematica versions. DSolve[{x'[t] == k x[t]^p, x[0] == c}, x[t], t] On one Mathematica, it produces a solution, but not in the other. There are no autoloaded packages on either of the machines. Under Mathematica 7.0.1.0 (Lenovo ThinkPad ... 4 Jun 2010 08:06

Histogram using FrequencyData in V7?
Hi, I'm trying to plot a Histogram given a list of (value, frequency) pairs. It looks like the old package function Histogram will allow this using the FrequencyData option, however, this option has been removed from the built-in implementation in V7. Does anyone know why this was removed, and whether there is a... 5 Jun 2010 08:07

DateListPlot (Margins? or something?)
Group: This is driving me nuts. I recall using ContourPlot a while back and finding an option to eliminate the 'padding' around the plot (i.e., between the plot and the frame), but can't find my previous work. Grrr... Does anyone know what option I'm thinking of? (And do you know if it will also work for Date... 5 Jun 2010 08:07

Symbolic integrals simplification
Hello everyone, I have symbolic expressions like Integrate[a*f[t],{t,0,y}] and I want Mathematica to write it as a*Integrate[f[t],{t,0,y}] i.e. whatever does not depend explicitly on t is a constant which can be factored out of the integral. How can I do this ? TIA ... 4 Jun 2010 09:12