Questions about how Mathematica evaluates expressions, tracing evaluation (Trace*), handling expressions in unevaluated form (Hold*, Unevaluated), nonstandard evaluation, etc.

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0answers
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How to ContourPlot a Table? [duplicate]

Possible Duplicate: Why is ContourPlot not displaying this curve? Why do I have to put Evaluate[] here I'm trying to plot certain contours of a function $f:\mathbb R^2\to\mathbb R$. What I ...
1
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2answers
153 views

Why does Evaluate[a[[1]]]=0 assign a value to a variable while a[[1]]=0 doesn't?

I'm trying to do a small page counter with Mathematica, for leting me know about my reading progress on some books. I'm stuck on a problem: ...
2
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3answers
151 views

Function to preserve evaluation on display?

I'm looking for a function that applies the following behavior to an expression: -When the expression is given as the full input, or as part of a function that cannot be evaluated, it remains in ...
5
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1answer
181 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 ...
6
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1answer
291 views

PlotStyle does not work when plotting a non-evaluated list of functions [duplicate]

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. ...
4
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2answers
205 views

Evaluating a Recursive Expression

Why does this raise an error ...
9
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1answer
91 views

Different behaviour of ValueQ inside and outside of a loop

I need to store a rather big number of variables and I tried to do that by storing each variable as Z[n] with varying n. I guess this was not my best idea. The first problem I encountered is when I ...
17
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1answer
650 views

How can I set a keyboard shortcut to run a command?

I want to use this to add a keyboard shortcut to an undo function I wrote. The basic problem is the following: I have a command, let's say x=1, and I want to run ...
8
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2answers
2k views

How do you force a decimal output? [duplicate]

I have some very small values such as 2.601519253*10^-8. I'd like to output these values to CSV for another program to work with. I've tried N[value, 50], but Mathematica still insists on producing ...
10
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2answers
193 views

Return partial result when MemoryConstrained aborts NDSolve

I use NDSolve to solve a large set (~400) of coupled ODEs. Sometimes, the memory (~4GB) gets filled up, and my computer becomes impossible to work with, because it ...
9
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1answer
246 views

Get the name of a symbol passed to a function

I'm trying to get the name of a symbol passed to a function with this: f[x_] := {SymbolName[x], x} SetAttributes[f, HoldFirst] x = 5; f[x] But ...
7
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4answers
222 views

Button's command is not evaluated in iteration

I wish I didn't feel like a newbie after several months, but... If I enter the following: Table[ Button[ "Number: " <> ToString @ i, Print @ i], {i, 1, 5}] ...
7
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2answers
116 views

Obtain input expression from history without evaluating

I typed and evaluated an expression, but deleted it from the notebook. For instance, suppose it was In[1]:= Round@SessionTime[] Out[1]= 2 I now want to retrieve ...
4
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3answers
206 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 ...
5
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2answers
621 views

Possible to evaluate only selected cells?

Is it possible to evaluate only the selected cells programmatically that I am interested in? Say in current cell to bottom of the notebook, instead of evaluate notebook or cells?
3
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1answer
264 views

Why can't Mathematica parallelize this?

The following code makes mathematica print "ParallelTable::nopar1: [...] cannot be parallelized; proceeding with sequential evaluation." ...
5
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5answers
575 views

Prevent Part[] from trying to extract parts of symbolic expressions

If you have a list, e.g. {1, 2, 3} then you can extract the $k$th part using Part (...
8
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1answer
130 views

Prevent Plus from threading InterpolatingFunction

For an InterpolatingFunction $y:\ \mathbb{R}\to\mathbb{R}^2$, Plus is unaware of this, so when I do any modifications to it in ...
2
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2answers
159 views

Updating a tracked symbol inside Refresh?

I have some code inside a Manipulate, whose goal is to allow the user to edit the upper half of the matrix while keeping it symmetric at all time. The minimal code ...
5
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2answers
4k 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 ...
14
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2answers
249 views

How can I access a variable in one evaluator from another evaluator?

I have two notebooks, each with a different kernel. Is there a way to grab the value of a variable in KernelA from KernelB?
16
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2answers
1k views

Difference between AbsoluteTiming and Timing

I need to evaluate the efficiency of my code. Therefore I would like to evaluate the time the code need for some calculations. Mathematica gives me two possibilities for this kind of evaluation: ...
11
votes
3answers
502 views

Labeling plots without evaluation

This is my first question here so please excuse my mistakes. Let us consider a rather contrived example: ...
2
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1answer
127 views

Implementing a For (?) or series or loop (?) for individual results for every x to n

I'm working on improving a modeling formula and have spreadsheets worth of data to use, but my work so far has been quite tedious. I'm essentially pulling 20 rows of data from each separate sheet of a ...
4
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2answers
618 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: ...
5
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1answer
351 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 ...
5
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0answers
147 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 ...
4
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1answer
65 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?
6
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2answers
542 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: ...
4
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1answer
125 views

Pre and Post in a Block[]

Why does Block[{$Pre = ( 1 + #) &}, 1] produce 1 while ...
12
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2answers
410 views

Preventing Numerical value from being evaluated

I have searched stackoverflow (and comparable pages) for quite a while now (got redirected from there to this specialized stack), and I surrender. I am trying to evaluate an expression that is small ...
7
votes
1answer
189 views

How can I have interruptible computations inside a manipulate?

Here's a perfect example of my problem: Manipulate[Pause[n], {n, {1, 10}, ContinuousAction -> False}, SynchronousUpdating -> False] It is illustrated by ...
14
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1answer
390 views

Using Evaluate and Evaluated -> True in Plot

A few use cases: (1) This, as expected, returns (almost) immediately: f[x_?NumericQ] := Evaluate[(Pause[1]; x)] Plot[f[x], {x, 0, 1}] (2) This takes ...
1
vote
1answer
171 views

Skip one step of the loop if there is an NIntegrate::eincr message

Is there a possibility of skipping one step of a loop if in this step there appears an error like NIntegrate::eincr? After skipping, the loop should go to the next ...
0
votes
1answer
67 views

How can I restrict a notebook to evaluate only if I am user 'root'?

I am playing with openCL on Linux with an AMD gpu, and due to a glitch in the driver, I need to be 'root' to get stuff to work. Installation question here.
11
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2answers
253 views

can a ColorFunction have side effects?

Can anyone explain this (to me) odd behavior. If I run this code once (fresh kernel) it works as intended. ...
13
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5answers
634 views

How are parameters evaluated for a Plot in Manipulate

I am trying to get my head around how Manipulate evaluates functions in a Plot. I have read the introduction to Manipulate, and introduction to Dynamic, but I still ...
1
vote
2answers
137 views

How can define a set of nested parameters

I would like to know how I to define a function with a nested set of parameters (or whatever you would like to call it). For example, how would I get the following function ...
5
votes
3answers
246 views

First evaluation fails

I am fairly new to Mathematica (version 7), so please bear with me... I have duplicated, in Mathematica, a program that I originally wrote in C (it generates OEIS sequence A191837). The problem is ...
7
votes
2answers
211 views

Why does the name of a pattern affect the result of a transformation rule?

I was playing a little dirty, trying to get a template for defining a Curl[] operator. I wrote the following rule, which I knew was going to spit out a few ...
13
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1answer
298 views

Evaluation indicator for a notebook

I have a GUI with a number of TabView and other Manipulate controls. Sometimes clicking from one tab view to the other can take ...
1
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2answers
98 views

What is the default file path used by the Put function and how do I pre-evaluate an expression to use in Put?

I have a problem of trying to store some output in an external file. In one note book I define a function f[x_]:=AdvancedCalculation, where this function generates ...
0
votes
1answer
132 views

Slow Dynamic Button Does Not Print [duplicate]

Possible Duplicate: Why do buttons with ChoiceDialog freeze the front end? Why is SystemDialogInput failing to return a save file path? Evaluation inside Button stops after some seconds I ...
4
votes
1answer
129 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] ...
13
votes
2answers
290 views

How to make use of NumericQ[x] = True (and use it safely)?

Basic Issue: I'm trying to understand the proper use of NumericQ's "magical" capabilities. Please consider the examples below. Actual question and some links are ...
1
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1answer
198 views

Particular solutions of a Differential Equation not evaluated in a given case

Below first case which gives particular solutions of an OED correctly: ...
7
votes
2answers
175 views

Keywords to find documentation for this syntax

Mathematica allows this syntax, but I cannot find any documentation (or books) that discuss the various uses/advantages of it ...
13
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1answer
434 views

Unique[] symbol not properly tracked

In a nutshell, why does this work (change y and see how the value updates) ...
5
votes
1answer
228 views

Parts of Module body evaluated in external scope?

I have an expression that suggests that some expressions in a module body are dragging in definitions from outside the scope in a surprising way. First, consider a symbolic constant, ...
15
votes
1answer
284 views

Polynomial expectations of generic distributions

Summary Polynomial expectations depend only moments and cross moments of a multivariate distribution. I would like to use Expectation to compute polynomial ...