Questions about how Mathematica evaluates expressions, tracing evaluation (Trace*), handling expressions in unevaluated form (Hold*, Unevaluated), nonstandard evaluation, etc.
5
votes
3answers
101 views
Applying a function with the HoldAll attribute inside NestList
I'm trying to write an update function, which can be applied to a list and then to NestList it.
As the function has to manipulate the given variable I figured I ...
5
votes
2answers
143 views
Graph does not evaluate some options when not displayed
How can I force Graph to evaluate all its options without actually displaying the graph itself?
Evaluating the following code ignores the ...
5
votes
2answers
237 views
Evaluate while external command is being run [duplicate]
Possible Duplicate:
Computing Many Slow I/O Operations
I'm launching an external command with the Mathematica front end that takes two arguments:
...
5
votes
2answers
180 views
Problem with ParametricPlot of multiple Curves
I have written a function f[Ne,t,T], that gives back a list of results when evaluated with numeric values of the variables Ne, ...
5
votes
1answer
113 views
Changes in Handling of Real Zeros
I recently upgraded from Mathematica 5 to Mathematica 8 and I have a number of notebooks that no longer work correctly. The problems relate to the use of units. I don't need complicated unit ...
5
votes
1answer
116 views
PlotStyle does not work when plotting a non-evaluated list of functions
When a list of functions is passed to Plot in an unevaluated form (e.g. with Through), the result is a plot with single color.
...
5
votes
1answer
71 views
how to print stack trace when TimeConstrained times out
According to the documentation, TimeConstrained generates an interrupt which interrupts the computation. This interrupt is treated just like an abort, at least in ...
5
votes
0answers
65 views
Every second evaluation in notebook front end is slow
I'm having a rather baffling problem that Wolfram was unable to help me diagnose, and I'm hoping one of you geniuses in residence here can figure it out. (I don't get access to the Technical Support ...
5
votes
1answer
129 views
Strange Behavior with RegionPlot
Consider the following code.
RegionPlot[Print[{x, y}], {x, -2, 2}, {y, -2, 2}, PlotPoints -> 2]
...
4
votes
3answers
314 views
All curves in plot have the same style. Cannot be fixed with Evaluate[]
Usually, when I plot multiple curves in Mathematica
Plot[{x,x^2,x^3},{x,0,1}]
they are given different colors. However, if I try to construct a list inside the ...
4
votes
2answers
175 views
Is there a way to show the details of a numerical computation?
I have recently started using Mathematica as a calculator while teaching (definitely overkill, but I try to use as few tools as possible). I would like my students to be able to trace simple numerical ...
4
votes
4answers
203 views
Efficiently finding the positions of a large list of targets in another, even larger list
I have a big list. It contains nearly 60,000 sub-lists. It's structured like
bigList= {{x1,y1,z1},{x2,y2,z2},{x3,y3,z3},.....,{x60000,y60000,z60000}};
...
4
votes
3answers
293 views
Why the difference?
When I do the double sum using the sigma notation I get
$$1 + \sum_{n=0}^{\infty}\sum_{k = n}^{\infty} \frac{1}{(k+2)k!}$$
$1 + e - \cosh[1]$
When I do the sums as below, I get the expected ...
4
votes
3answers
138 views
Keep function range as a variable
Plot[2*x^2 - x + 2, {x, -1, 1}] plots a function of x from -1 to 1. As far as I can see, I cannot "save" this range in a variable:
...
4
votes
1answer
213 views
Strange Error in Bifurcation Diagram:
I am attempting to plot the bifurcation diagram of the tent map
$$
f(x):=2\alpha
\begin{cases}
x, & 0<x<1/2\\
1-x, &1/2<x<1,
\end{cases}
$$
i.e., the plot $\alpha$ vs. the limit ...
4
votes
2answers
138 views
Why is CityData[All, “Coordinates”] failing?
When I evaluate
CityData[All, "Coordinates"]`
Mathematica returns
{Missing["NotAvailable"], Missing["NotAvailable"]}`
but when I evaluate ...
4
votes
2answers
183 views
How to make a function that evaluates an expression?
I'm trying to make a function where the input is an expression, but somehow it just won't be evaluated. For example, this little function doesn't work:
...
4
votes
1answer
245 views
Can a Table iterator “leak” into a Module?
I want to repeatedly call a module by using a Table statement. When I use an i iterator in the Table command calling the module, I receive the error message ...
4
votes
3answers
165 views
How can I create a custom control which evaluates to a list of values or replacements?
I have a set of variables which are used in various places in my calculations (solving a system, initial conditions, etc.). In order to make this easier to deal with, I want to make a control-like ...
4
votes
1answer
97 views
4
votes
1answer
137 views
Why does Dynamic output cause CPU usage when onscreen?
I write such a line in Mathematica:
{Slider[Dynamic[s]], Dynamic[f[x_] := s*x]}
After evaluation, the CPU immediately runs at full power. And if you scroll the ...
4
votes
1answer
136 views
Assumptions seem not to be considered
In the following a,b is a probability distribution, i.e. a+b==1 with ...
4
votes
4answers
151 views
Unexpected behavior of Unevaluated
Maybe it is about time I read some proper text about the main loop. Maybe I should not care (so much) about Unevaluated (as Leonid suggests). But I think this is an interesting question anyway.
This ...
4
votes
1answer
94 views
Identical code, different answers?
I'm having some trouble with identical code giving different answers. On a fresh kernel (MM 9.0.0.0, Windows 64-bit), running the same code, copy-paste, gives two different answers:
...
4
votes
2answers
132 views
4
votes
2answers
158 views
Setting a lower limit on calculation time
Sometimes it can come in handy to set a lower limit for a calculation. Consider for example an animation that is generated by some infinite loop, which would run way too fast to display properly for ...
4
votes
1answer
154 views
Behavior of expression evaluation in Plot
I'm confused with Mathematica's way of parsing expressions. I've been struggling with this for a while and never found an exhaustive answer, sometimes things don't parse the way I think they would ...
4
votes
1answer
120 views
Tweaking Prime[n] to return 1 when n==0
I manually evaluate this cell to set Prime[0]
Unprotect[Prime]
Prime[0] = 1
Protect[Prime]
I manually evaluate this cell to reset Prime[0]
...
4
votes
1answer
106 views
Evaluation order control
This question is related to Evaluation order of Button[]'s action
Concusion was, Button[]'s actions are evaluated in preemptive link so "the code that needs ...
4
votes
0answers
46 views
Problem with inequality using refine
I am using inequalities to follow some line of reasoning in Mathematica and I came across a problem I can not explain to myself. Does from a>=0 and b>=0 not follow a+b >= 0? How does Mathematica ...
4
votes
0answers
83 views
Context “Unique to This Notebook” makes variables black even if they're not defined?
I'm trying to use this technique to keep variables separated between different notebooks. It seems to be working fine, except that variables turn black as soon as they are evaluated — any ideas why ...
3
votes
3answers
233 views
Help on evaluation control?
I want to plot series of slopes:
x, 2x, 3x, 4x, 5x, 6x...
I'm trying to do this:
...
3
votes
4answers
1k views
Mapping multiple parameters of a function to specific values
I am a little bit confused by the documentation for Apply (@@).
I want to define a list of parameters, for instance:
...
3
votes
2answers
199 views
Efficiently evaluating a held expression directly from a list
I am able to evaluate a held expression that I have put on a list by:
ReleaseHold[expressionList[[1]]]
and
...
3
votes
2answers
954 views
Simple ways to evaluate a derivative at a point?
The contrast in behavior between, say,
f[x_] = Sin[x^2];
f'[2]
vs.
u[x_, y_] = Cos[x + y^2];
has always bothered my ...
3
votes
1answer
68 views
Evaluation order of Button[]'s action
it looks like it should be well known issue but I haven't found answer anywhere.
Please tell me why the result (after clicking) of this:
...
3
votes
1answer
168 views
Log function - why is Log[b,b] not being evaluated to 1?
Have been experimenting with the Log function to demonstrate simple Log relationships such as Log[xy], Log[x+y] etc.
...
3
votes
2answers
85 views
Turning evaluation off
I am making a directed graph, but Mathematica keeps trying to evaluate my labels. I know that I can just use " ", but I have a lot of input. Is there a way to turn evaluation off?
...
3
votes
2answers
79 views
UpValues evaluation with Dot operator
I would like to simplify some database notation, and I'm doing some tests with UpValues for that.
For example, if I set this Upvalue fot tab1:
...
3
votes
1answer
109 views
Set promotes Rule to RuleDelayed?
In mentally building a model of how Mathematica works, I naively expected Set to create a Rule in a symbol's ...
3
votes
1answer
54 views
Stop TradtionalForm evaluating expression
I'm trying to get this expression to display as typed instead of evaluating the 1/1.121.
...
3
votes
1answer
47 views
How can I kill one evaluator from another?
I have a kernel named A in one notebook and other notebook with kernel B, how can I kill B from A?
3
votes
1answer
224 views
How is the Mathematica kernel structured internally, and how does evaluation work?
There is so much information available for Java--the internal details of (for example) the JVM memory manager are well-documented, and the performance considerations arising from its interaction with ...
3
votes
1answer
166 views
FunctionInterpolation Errors / Question re Evaluation Order and Options
I have using Mathematica functions that takes a Cartesian coordinate relative to the Earth (xyz) and converts it to a latitude, longitude, and altitude (lla). And here it is:
...
3
votes
1answer
99 views
Manipulate a Plot that contains a variable that contains symbol
This snippet
mm = m
Manipulate[{mm, Plot[mm x, {x, 0, 1}]}, {m, 0, 1}]
(m is not defined anywhere) produces a sadly fixed ...
3
votes
0answers
178 views
A is fast, B is fast, but together they're Mathematica-crashing slow?
I'm trying to do something with finding solutions to a quantum mechanics problem with n wells. If there are 40 wells, I need to find the solution to an equation in the form:
...
2
votes
2answers
101 views
How to make Mathematica returns the exact expression I typed
I'm using Mathematica to compare some constants. Before playing around with those constants, I would like to check that I didn't make any mistake in typing them. So my question is the following: "What ...
2
votes
3answers
115 views
Alternative to using global variables in functions?
Often times I find myself using unevaluated variables (i.e. they show up blue) as dummy variables in whatever I'm returning such that I can evaluate them as needed later on.
A simple example is as ...
2
votes
2answers
82 views
Evaluating Polynomials at Grid Points
I am continuing my quest on B-splines. The code below builds a 5x5 matrix out of B-splines, using the BSplineBasis[] routine.
I now want to evaluate the polynomials that are stored in each matrix ...
2
votes
2answers
93 views
How do you configure Mathematica 9 to automatically evaluate all notebooks?
I have a Mathematica 6 course that I am using in Mathematica 9; there is no updated version. Every time I open a notebook I have to go to the Evaluation menu and click on "Evaluate Notebook". Is there ...
