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

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Mathematica Not finding Eigenvectors? [duplicate]

I have the following matrix: mat = {{-60., 0., 2.1*10^-35 II + 2.1*10^-35 (-1. II + Istar), 2.1*10^-35 II + 2.1*10^-35 (-1. II - 4.7619*10^6/Istar)}, {-6.4*10^22 II - 6.4*10^22 (-1. II - ...
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0answers
15 views
-2
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1answer
365 views

Why doesn't Mathematica evaluate this limit? [closed]

I am trying to evaluate a few limits in Mathematica, and I can only get it to evaluate them in certain cases. I don't fully understand the evaluation order and when it substitutes numerical values in ...
3
votes
1answer
66 views

Why doesn't Mathematica abort evaluation when I tell it to?

This frequently happens to me. I'll have some code, execute it, and realize it's taking a long time. My PC isn't frozen, and Mathematica itself isn't even frozen: I can select stuff in the notebook, ...
6
votes
2answers
147 views

What is the Difference Between Rule (->) and RuleDelayed (:>)?

I am new to Mathematica so this question may seem rudimentary. Sorry for that! :) I want to implement the well-known property of Kronecker's Delta $$\Sigma_{i=1}^{n} a_i \delta_{ij}=a_j,\quad 1 \le ...
4
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4answers
120 views

Working with ScheduledTasks inside DynamicModules

I have a question - is it possible to run ScheduleTask[] inside DynamicModule[]? What I have tried so far: ...
6
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1answer
200 views

Where does a package have to be loaded?

I'm trying to solve a very tricky issue in my function. The function needs the NDSolve`FEM` framework. Here is a minimal example: ...
16
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2answers
609 views

How do I get Mathematica to return a function call unevaluated?

How do I get Mathematica to return a function call (conditionally) unevaluated? I expect this may use the slightly-mysterious Hold function. As a toy example, ...
1
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2answers
154 views

After NumberForm I cannot apply a Sine function. Why?

After NumberForm I cannot apply a Sine function. Why? This works: sol1 = x /. Solve[x^2 - 3 == 0, x] Sin[sol1] Output = $\{-Sin[\sqrt{3}],Sin[\sqrt{3}]\}$ Also ...
1
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2answers
60 views

Unpacking NumberForm expressions

Given a NumberForm expression, e.g.: NumberForm[N[Pi], 10] How does one get the underlying numerical expression (short of ...
5
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1answer
81 views

Blocking dialog with a blocking child dialog

Suppose I have a DialogInput, in which there is a Button. The Button can trigger another <...
23
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5answers
496 views

Result about Context is inconsistent with the description of “Power Programming with Mathematica”

x = 5; temp`x = 6; Begin["temp`"] {x, Global`x, temp`x} The result in my Mathematica session is {5,5,6}, but it's ...
9
votes
2answers
132 views

Evaluating summations involving Fibonacci numbers in terms of Fibonacci numbers

There are many summations involving Fibonacci numbers which Mathematica 10.4 is able to evaluate directly in terms of Fibonacci numbers. For example, Mathematica evaluates the summation given below as ...
0
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0answers
33 views

Mathematica won't evaluate on the first run & problem with code highlight

When I start Mathematica, the first evaluation always takes forever even it's as simple as x = 2, and when I halt the evaluation with ...
1
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2answers
50 views

Chains of approximate numeric equalities

Mathematica considers two numbers equal if "at most their last seven binary digits" differ. For example: ...
9
votes
2answers
298 views

Remove versus ClearAll

What is the difference between Remove and ClearAll? I thought that "not being recognized by Mathematica", which is the effect ...
14
votes
4answers
2k 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 <...
3
votes
1answer
58 views

How to wait a Cell in a Notebook to be executed until another Notebook's Cell expressions executed?

I have two Notebooks and I call the second Notebook from the main but main Notebook's expressions continue executing. I want them to wait until the second Notebook's expressions execution is finished! ...
1
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1answer
89 views

Evaluation of a Notebook

I am new to Mathematica so I do apologize if my question is too elementary. In the start of my notebook, I want to make sure that any previous definitions are wiped out so I use the ...
10
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2answers
423 views

Nothing not behaving as expected?

I was thinking that Nothing was doing the same job as the vanishing sequence ##&[]. Yet this exemple shows it doesn't. ...
0
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0answers
32 views

The problem encounterend while calling a sub notebook from the main notebook

I have two notebooks; one of them is the main notebook which will call the second notebook several times in a loop and inside this loop, matrix called as ALLB, defined in the main notebook, will get ...
3
votes
2answers
133 views

Multiplication non-deterministic?

I have two vectors of 134 elements each ($mu$, and $gt$). $mu$ contains Integers, and $gt$ contains machine precision Reals. I execute the following simple expression multiple times without changing ...
0
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1answer
43 views

How to use Set correctly

My codes are shown in the picture attached. I'm writing codes for numerical calculations frequently, and I think it looks neat and clear to organize input parameters in the form of table. For example,...
18
votes
2answers
314 views

Understanding evaluation and typesetting

Background So, one could be surprised by the fact that: Hold @ Grid[{{1, 2}}] (*or*) Hold @ Graphics @ Disk[] This issue and methods of prevention are ...
1
vote
1answer
84 views

How to define a function which takes another function as input in Module

Let $f$ be a function of $n$. I would like to define a function $A$ with module which takes $f[n]$ as input. So for example: ...
3
votes
1answer
102 views

Can evaluation show what was evaluated along with results? [duplicate]

After I write and evauate the following lines in Mathematica: a = 1 b = 2 x = a + b It will show only the result : 3. I want mathematica to show the following ...
0
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0answers
39 views

Evaluating a function after simplifying to avoid infinite expressions

My Poly[j_, s_] function simplifies to a polynomial for all j. So I defined a PolySim[j_, s_] = Simplify[Poly[j,s]] function. However, if I try to evaluate PolySim[j,0], since this is PolySim[j,0] = ...
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2answers
124 views

NIntegrate evaluates its 1st argument while it has the attribute HoldAll?

NIntegrate owns the attribute HoldAll: Attributes@NIntegrate (* {HoldAll, Protected} *) ...
9
votes
1answer
124 views

How useful is $EvaluationEnvironment?

Bug introduced in 10.0 and persisting through 10.4.1 A support case with the identification [CASE:3618534] was created. [...] I filed a report with our development team raising the issues [.....
1
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0answers
41 views

Using Replacement Rule on Part of List? [closed]

Why can't I use a replacement rule to replace a variable name standing in for the index of a list? For example: myList={1,2,3,4,5} myList[[index]]/.index->3 ...
0
votes
1answer
114 views

How to speed up my code for plotting purposes?

Below is my code in order to produce a numerical expression for the final function that needs to be plotted. I have tried to see the output of each successive expression by running the code and ...
7
votes
3answers
82 views

Kernel randomly aborting

Bug introduced in 10.0 and fixed in 10.3 So after 2 days of trying to figure out what's going on, I figure I should post here as I don't have enough knowledge about the Mathematica evaluation ...
3
votes
1answer
80 views

Generate assignment code to symbols from string

I want the function to take in string, then assign a value to its corresponding symbol. An implementation using ToExpression is ...
6
votes
1answer
57 views

Partial evaluation of symbols with non-inert OwnValues

Background: there are many, many questions here about the infamous ::setraw error. More often, than not, they have to do with repeated assignments to symbols. Here's the code: ...
10
votes
1answer
111 views

Evaluation leak from Dynamic in Button's action

a = 1; Button["Print", a++] Button["Print", Dynamic[a++]] Button["Print", Dynamic[a++];] Button["Print", {Dynamic[a++]}] Dynamic @ a The second ...
3
votes
2answers
157 views
0
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1answer
39 views

Replace argument of delayed function before it evaluates [duplicate]

How should I use replace so that f[x_] := x^2 Replace[f[3], 3 -> 1] OUT = 9 evaluates to 1, instead of 9? This way, the replacement of the argument is done ...
0
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1answer
34 views

Forcing evaluation of LinearSolve [closed]

I have a linear solve function: ls = LinearSolve[MatrixForm[Transpose[basisNScoeffs]]]; Which I then use to generate a table of solutions: ...
1
vote
0answers
36 views

Prevent infinite product from trying to evaluate?

Consider an expression involving several infinite and non-infinite products, like ...
0
votes
1answer
76 views

Mapping over function's several parameters regions [closed]

About this post: Mapping multiple parameters of a function to specific values I wonder if the parameters a and b have ranges ...
15
votes
2answers
388 views

Shell Emulation inside Mathematica

I am trying to create a Mathematica/shell syntax hybrid. I would like the following command wget -qO- "http://google.com/space line break\"" $var to be ...
3
votes
1answer
467 views

Gâteaux (directional) derivatives and higher order differentials of a functional

I would like to calculate the Gâteaux derivative of a functional (i.e. a function depending on functions). A simple example for the Dirichlet functional: $L(u(x))=\int_0^1 \frac{1}{2} (u'(x))^2 dx$ ...
2
votes
1answer
78 views

Help on order of evaluation within plot function

it is my first time asking a question here so please let me know if there's anything I should be doing that I'm unaware of. I'm sure the answer to my question already exists on the site but I'm having ...
0
votes
0answers
35 views

Creating a non-zeta-ified sum

The expression Sum[i^(-s), {i, 1, ∞}] evaluates to Zeta[s] But, of course, this is not strictly correct as ...
8
votes
2answers
70 views

How do I SetDelayed $Assumptions

For some reason, $Assumptions := (Print["y"]; x > 0) evaluates the RHS immediately. I have code in which $Assumptions ...
0
votes
0answers
42 views

Parallelization and efficiency improvement

Hey i am new to mathematica and at the moment i am writing some test code. It works but it is unrefined. I try to make it more efficient by using parallelization or other techniques. I wanted to ask ...
5
votes
1answer
501 views

Is there a method to send different Cell evaluation to different core?

I am running Mathematica on a computer with multi CPU and every CPU has multicore. I am wondering if there exist a method to send different cell evaluation to different core? So if I already have a ...
1
vote
1answer
111 views

Evaluate pure function through round brackets

In have some matrices of pure functions or numbers which I multiply by other matrices or vectors. I would like the functions to be evaluated in the result, but all that I get is something like this: <...
0
votes
0answers
21 views

How to make an expression in this case evaluated one step and stop there? [duplicate]

I wonder how to make Symbol@"m" evaluated once so that it becomes a symbol m which is ready to be assigned again. ...
2
votes
1answer
55 views

recursively structuring a multivariate numerical optimization

Suppose that I want to partition the unit interval [0..1] into four subintervals whose max length is as short as possible. I can ask Mathematica to: ...