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

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16
votes
2answers
904 views

How to restart computation when kernels die?

When an important process needs to be kept alive, there are monitoring tools to restart them if they die (e.g. god tasks in ruby), in my case I have an overnight scraping task that I need to have done ...
0
votes
1answer
51 views

Alter evaluation order when applying scalar multiplication to function

Consider the following program: g = 2f; g[x] (* (2f)[x] *) Is there any way I can change the above expression to have it return ...
3
votes
0answers
74 views

Is there an analogue of Evaluated->False (in FindRoot) for FindMinimum?

I guess functions like FindRoot, FindMinimum, etc puts the estimation number into the expression, and then do other ...
0
votes
2answers
45 views

Unevaluated derivatives of known functions after replacement

I want to make the following replacement work correctly: Array[(2 D[xM[[#1]][t], t] * D[xM[[#2]][t], t]) &, {3, 3}] /. {xM -> {Sin[ω t], Cos[ω t], 0}} ...
3
votes
1answer
99 views

Fast evaluation of a function in many points

I need to feed to an external program a number of points (in Complex128 format) generated from the numerical evaluation of some function, e.g. $e^{i ...
1
vote
1answer
219 views

new kernel for notebook

I know I can create a new kernel for my notebook from the evaluation menu but is there a command for this? I'd really like some of my notebooks to startup their own kernel as the first line of code.
4
votes
2answers
107 views

Manipulate in modal mode

It is sometimes convenient to use Manipulate to set up global values which are to be used in the rest of the notebook. In such cases one can select and run the ...
0
votes
0answers
53 views

What makes items with head `Function` different?

I apologize beforehand for the muddleheadedness of this question. It reflects the fact that I'm trying to interpret outward "behaviors" of Mathematica expressions without having any understanding of ...
0
votes
0answers
43 views

Order of evaluation for numeric functions

I'm trying to plot a 3D vector field to illustrate an electric field of a uniformly charged disk, and I used Manipulate to change the radius R of the disk to see ...
5
votes
5answers
217 views

Nested function with an increasing argument

If, for example, I have a nesting function like Nest[1 + x^n (#) &, 1, 3] it gives the result ...
3
votes
0answers
114 views

Assign variables from list inside With or Module

I have found that it is possible to assign variables from lists, as follows. r = {1, 2, 3}; {a, b, c} = r; b 2 However, ...
0
votes
1answer
119 views

Plotting two variables indirectly dependent on each other

I have the following system of linear ODEs for "i" number of species "c" migrating in "j" number of habitats: ...
19
votes
2answers
359 views

What does f_[whoCalled]^:=f really mean?

I came across the following post by John Doty in this Google Groups discussion: On Friday, January 11, 2013 8:23:16 PM UTC-7, amzoti wrote: It is clear the Mathematica uses Lisp as one ...
2
votes
0answers
52 views

Import names into notebook namespace [duplicate]

I have function that at some point has list of strings (e.g. {"apple","pear"}) and I want to declare (initialize) those variables in notebook namespace to default ...
1
vote
0answers
34 views

Save a Mathematica notebook evaluated [duplicate]

My notebooks can take some time to evaluate and by quitting Mathematica, I have to reevaluate every definition I've made once I restart Mathematica. Is there a way to tell Mathematica to save the ...
0
votes
0answers
80 views

Skipping sections of a notebook automatically

I have a notebook which allows to set some parameters at the start, and then does computations depending on these parameters. It is a long notebook and for readability it is broken up into sections ...
4
votes
1answer
51 views

How to adapt MSPToExpression function in $PrePrint?

I am introducing the mathematica Security (MSP module) to our system. The Document suggests use MSPToExpression as followed: ...
10
votes
1answer
122 views

Use EvaluationCompletionAction to notify me only after long evaluation

Is it possible to use the option EvaluationCompletionAction to notify me (e.g. with a Beep[]) when an evaluation that took ...
1
vote
1answer
49 views

Evaluation of InverseFunction at the boundaries of its domain

Folks, I want to numerically evaluate a InverseFunction h[x] close to the edges x5 and ...
8
votes
6answers
2k views
1
vote
1answer
39 views

Please explain this pattern/Message related issue and help with finding workaround

I attempted to clean up my code and also add messages to functions if they are called with wrong arguments. This introduced some error which I tracked down to the following: ...
10
votes
4answers
336 views

How to take and evaluate a specific part of a list without evaluating the rest?

I have a large list, for example, lis = {x + y, x y, Sin[x] y + Exp[y], x^2 y} and its elements depend on variables x and ...
2
votes
0answers
43 views

Executing selected code [duplicate]

In current Mathematica interface, if I select some piece of code and press CMD + Shift + Enter, the code is evaluated in place. Replacing the selected part by the evaluated version. The question is: ...
0
votes
0answers
70 views

Memoization and upvalues

Can I store an algorithm to one variable and the result as an upvalue to another? With regard to the problematic code below (real algorithm and argument test omitted), I would like to store the ...
1
vote
1answer
55 views

Creating a keyboard shortcut to change the Style of text [duplicate]

I'm editing a very long text in a Mathematica notebook and I'm using the "Article" stylesheet. In this text, code is highlighted using ...
6
votes
1answer
264 views

Dynamic and Refresh

If I am not mislead by my memory, in Mathematica 6 a function Refresh was introduced, having the options UpdateInterval and ...
1
vote
1answer
43 views

Showing updating message in Dynamic with UpdateInterval

I am creating an interface which needs to repeat an operation every few seconds. The operation itself is expensive but faster than the update interval of the interface. I would like to have some ...
10
votes
2answers
174 views

stop notebook evaluation when Assert fails

I would like a notebook evaluation to entirely stop when an Assert fails, without quitting the kernel. Is this possible (e.g., by setting ...
2
votes
2answers
86 views

PasteButton: Pasting expression name without quotation marks?

I am struggling to find a way to use PasteButton to paste the name of an expression (in particular a list) without showing the contents of the expression or without ...
2
votes
2answers
68 views

How can I use an InputField value as a variable name to save to?

I'm trying to save some settings and results from Manipulate, and I want to be able to save them to different variable names. The code I have is something like ...
22
votes
2answers
3k 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: ...
23
votes
1answer
2k views

A one line proof that one is zero using Mathematica 10

a = (Sqrt[2] + 1) (Sqrt[2] - 1) - 1; {a/a, Simplify[a]/a, b/b == Simplify[b]/b} {1, 0, True} This one line "proof" that ...
14
votes
3answers
391 views

Clever use of DownValues, or failure to understand the “Mathematica Way.”

I needed to look at the changes in the values of about 4000 items from one year to the next. I have a table with identifiers and values for each year. Not all of the items are in each list. The ...
5
votes
1answer
46 views
2
votes
1answer
117 views

How to properly define this function of function

I encountered real problem at first, and here is the toy example variable argument stored some expression that is generated from other parts of the program. I ...
1
vote
0answers
72 views

Meaning of Abs´? [closed]

A friend showed me the code below. r[i_] := {x[i, t], y[i, t], z[i, t]}; rji = r[i] - r[j]; solap = 2 a - Norm[rji]; FullSimplify[D[solap, t]] I'm unsure about ...
26
votes
4answers
1k views

Asynchronous evaluation: Is it possible?

Currently we have a limited number of ways to perform asynchronous evaluation. The most common is through Dynamic and ...
5
votes
2answers
103 views

Parallel function evaluation for minimal value

I am asking myself, if the evaluation of a function f looking for a minimal value over a discrete set of values can be parallelize (brute scan for a potential ...
1
vote
1answer
63 views

Resolving Error: Mathematica evaluation order on Lists

I have a table that is 27 x 27, each entry corresponds to an element from the periodic table. I use the replacement rules in element list to allow me to convert a list of elements into a list of ...
2
votes
3answers
6k views

Step-by-step definite integration

I am interested in obtaining the intermediate steps for rather straightforward symbolic definite integrations (e.g., from an elementary calculus text). As an example, for $\int_0^1 x\,dx$ I'd like ...
2
votes
3answers
115 views

Evaluation inside a Manipulate

Let's assume I have a symbolic expression, and inside a Manipulate I define the actual values: ...
1
vote
2answers
64 views

Plot of function-generated lists: Why does this workaround not work?

My problem is a classic one: I want to plot a function-generated list, and there's no way to pre-evaluate (because the actual function includes NMinimize and thus ...
0
votes
2answers
105 views
2
votes
1answer
83 views

Errors in plotting regular function

Suppose we want to define Tanh-function via exponent: th[x_] := (1 - Exp[-2 x])/(1 + Exp[-2 x]); FullSimplify[th[x]] Out[13]= Tanh[x] Then we define new ...
5
votes
2answers
256 views

Evaluate notebook from other notebook

I have a notebook ("notebook 1") which in the beginning sets some parameters, does something depending on their value and saves the result to a file, say: ...
1
vote
1answer
41 views

Aborting an evaluation automatically after a specified time elapsed

I use the following code to evaluate a series of notebooks: nb1 = NotebookOpen["C:\\Users\\....nb"]; SelectionMove[nb1, All, Notebook] SelectionEvaluate[nb1] ...
1
vote
1answer
51 views

How do I dynamically update “name” of Action Menu?

I have created an action menu that allows you to change the style of a cell. It works. However, I would like it to dynamically update the action menu "name". I can't get the name to refresh. ...
1
vote
1answer
64 views

Trace and SameTest in Union [closed]

This question is actually two question. First, I feel so stupid that I just don't understand the use of theSameTest option in ...