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

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2
votes
1answer
109 views

How to abort running evaluation?

I would like to implement a "Stop" Button into a program that basically consists of a loop. Unfortunately I do not how to interrupt the running evaluation. Minimal Example: ...
2
votes
1answer
306 views

kernel Local crashes during the course of a For loop

I want to find the minimum of the function r[x,p] subject to the constraint w[x,p,t]==0 (t ...
2
votes
1answer
104 views

What is “ (Dialog) Input [ ] := ” after evaluating a cell?

I have done a time-consuming run and calculation. After many hours ( about 7 hours!), the black color which shows that the cell is evaluating, turn into gray and a strange text appears like this : ...
2
votes
1answer
714 views

Why does Mathematica evaluate Sin[2.0] but not Sin[2]?

I can't understand why is it that In[88]:= Sin[2] Out[88]= Sin[2] while In[89]:= Sin[2.0] Out[89]= 0.909297 I even tried ...
2
votes
1answer
172 views

Piecewise function with user-input interval

I would like define a function g[data,bins,x] which is a piecewise constant function taking value data[[i]] in the range ...
2
votes
1answer
72 views

Evaluate only one from a set of procedures

Let's say I've got a list of procedures: {Print[1];, Print[2];, Print[3];} And I want to only evaluate 3rd one: ...
2
votes
1answer
134 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 ...
2
votes
0answers
43 views

Find the numerator of 6/8 [duplicate]

The statement Numerator[6/8] evaluates to 3. Numerator[Hold[6/8] does not work. What function NewNumerator[6/8] evaluates to 6?
2
votes
0answers
66 views

What is the difference between GenerateDocument and TemplateApply[NotebookTemplate[

Abstract GenerateDocument[ _NotebookObject ] seems to do the same what TemplateApply[ NotebookTemplate @ _NotebookObject ] ...
2
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0answers
186 views

Mathematica shift-enter problem

Would really appreciate if someone can help with this problem: When I first open a Mathematica note book, say you do 1+2 and press shift-enter. As expected, I get "3" as the output. Now suppose you ...
2
votes
0answers
65 views

$Epilog does not work when exit

The following code does work: $Epilog := Print@1; Quit[]; But if I close the document and exit WM or click QuitKernel, it does not work. Why?
2
votes
0answers
50 views

Timing of ParallelDo versus Do: simple example [duplicate]

I'm trying to understand why a simple do-loop takes substantially longer when done in parallel than sequentially: ...
2
votes
0answers
77 views

Assign a value to a variable without using Set or SetDelayed?

I supose probably yes, but at the end I assume that internally mathematica has to use Set or SetDelayed. Am I right? Background: I am developing a super simple phraser that takes a code description ...
2
votes
0answers
85 views

Assign variables from list inside With or Module

I have found that it is possible to assign variables from lists, as follows. In[1]:= r = {1, 2, 3}; In[2]:= {a, b, c} = r; In[3]:= b Out[3]= 2 However, if I try ...
2
votes
0answers
333 views

Lazy evaluation/loading of parts of an expression

Is it possible to have an expression x such that its elements are only evaluated when they are individually accessed, for example when evaluating statements like ...
2
votes
0answers
118 views

Strange double evaluation using MorphologicalGraph

(MMA 9.0.0 on Mac OS/X 10.8) Please consider the following snippet (this is as SMALL as I could make it -- my attempts at making a smaller repro-case eliminated the effect that I am investigating) ...
1
vote
2answers
57 views

Evaluating and Plotting Multiple Zero-Counting Functions

In work that I am doing, I am trying to plot multiple zero-counting functions, depending on how a parameter works. For example, if the zeros of one function are {1, 2, 3, 4, 5, 6, 7}, the zeros of ...
1
vote
1answer
1k views

The underlying process of Integrate[] [duplicate]

Integrate[x^4 E^-x^2, {x, 0, +∞}] Output: (3 Sqrt[π])/8 Can someone explain to me the specific calculation process ?
1
vote
4answers
117 views

Do not expand matrices in Mathematica calculation

Here is an example of a problem I'm having. Consider that I have defined: omega={{p[t]},{q[t]},{r[t]}} x={{a},{b},{c}} R={{1,2,3},{4,5,6},{7,8,d}} What I would ...
1
vote
2answers
224 views

How can I speed up this plot manipulation? Why does Evaluate not help?

If I were able to "Save" the computed inverse function somewhere and then plot it, the manipulation would become faster. As I understand, Evaluate should do the job, but for some reason it does not. ...
1
vote
3answers
88 views

Keep leading/trailing zeroes (like Defer except with numbers) in a given number

I'm trying to write a function that counts the number of significant figures a given number has so I can ensure my calculations are rounded correctly; however, I am having a lot of trouble preventing ...
1
vote
3answers
60 views

Controlling the evaluation of other arguments in pure functions [duplicate]

I have a piece of code where I would like to do the something like the following: ...
1
vote
2answers
740 views

How to evaluate Modules in a notebook from another notebook?

I would like to create a notebook populated with several modules and be able to evaluate these modules by running a separate notebook. I have attempted several uses of the ...
1
vote
2answers
125 views

Evaluation of elements in a list and then sorting them

This is probably a simple problem, but I'm having a lot of issues with it because I'm unfamiliar with Mathematica syntax. I have a list ...
1
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2answers
760 views

Derivative of a spline approximation

To approximate an experimental data function $f(t)$ with $t \in (t_{min},t_{max})$ I used a cubic spline $s(p)=(t(p),f(p))$ with the parameter $p \in (0,1)$ and $p = t/(t_{max}-t_{min})$ by using the ...
1
vote
2answers
161 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: ...
1
vote
2answers
104 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 ...
1
vote
2answers
128 views

Evaluate a list

I have a function $f(x_1,\cdots,x_n)$ that takes $n$ arguments, and I would like to evaluate it using a list of lists $\lbrace\lbrace x_1,\cdots,x_n \rbrace,\cdots,\lbrace x_1',\cdots,x_n' ...
1
vote
3answers
122 views

How I create a 'TraditionalForm' expression in which only parts are evaluated?

I have an expression for the form Subscript[W, f[a, b]][c] = ρ^f[a,b]ω[c]ρ^-f[a,b] that I want to render in TraditionalForm ...
1
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2answers
129 views

Automatically evaluating related cells

I have the cells: In[1]:= l = 2 + 2; In[2]:= l >= 5 After evaluating them: Out[2]:= False Is there a way to evaluate ...
1
vote
2answers
211 views

How to get the absolute difference between two angles

I need a function that will give me the shortest separation between angles that range from -pi to pi. For example if I have two angles 3pi/4 and -3pi/4, I would like a function that will tell me pi/2 ...
1
vote
1answer
233 views

FindRoot with vector functions

I'm trying to solve a system of non-linear equations with FindRoot, and I get the answer, but also a ...
1
vote
1answer
183 views

Passing a joined list of symbols for Module or Block to treat as its own local symbols

The Question I'd like to write a function which itself takes a list of symbols, e.g. Foo[{x, y, z}] to pass to Module ...
1
vote
1answer
376 views

Why is evaluation Enter for Mac and shift+Enter for Windows? [closed]

Per the title, why is evaluation done using just the Enter key for Macintosh and shift+Enter for Windows? UPDATE Okay, I see the Mac keyboard's "Enter" key is actually labeled "Return", so by Enter ...
1
vote
1answer
117 views

Why does evaluating an integral within a Plot expression take so long? [duplicate]

I want to evaluate Plot[Integrate[Sin[((1 + 1/2) x)] (1/(2 Sin[(x/2)]) - 1/x), {x, 0, t}], {t, 0, 5}] but it takes ages to load on Corei3 computer with ...
1
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1answer
526 views

Forcing evaluation of ArgMax

How to force evaluation of ArgMax before its output gets used in Solve? Background: I'm trying to solve for the Nash ...
1
vote
1answer
42 views

problem about Root and Hypergeometric2F1

See these example, why does the output is different? ...
1
vote
1answer
50 views

How to achieve fun[Unevaluated[f][Unevaluated[x], Unevaluated[y]] in a more elegant way?

I have defined a function fun[f_[x_,y_]]. When I call it, I want to wrap everything by Unevaluated: ...
1
vote
2answers
100 views

Why does Mathematica not evaluate the difference recurrence using `RSolve` or `RecurrenceTable`?

Mathematica does not evaluate the following recurrence of two variables using RSolve and only echoes the input: ...
1
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1answer
79 views

A With and ContourPlot difficulty

Consider: sys = {u (1 - u + a v), r v (1 - v + b u)}; With[{a = 2, b = 3, r = 1}, Evaluate[Thread[sys == {0, 0}]]] Which gives the output: ...
1
vote
2answers
73 views

Assigning to the “local” version of a symbol

Compare Manipulate[c[1] = 1; c[1], {c[1], 0, 1}] with Manipulate[Do[c[i] = 1, {i, 1}]; c[1], {c[1], 0, 1}] The first case ...
1
vote
2answers
82 views

Pattern matching to head with HoldFirst

I want to define a function that only operates on expressions with a head from a given list, such as f[expr:(_And|_Or)] := Print["LHS is ", expr[[1]]]; This of ...
1
vote
2answers
82 views

Extract the real components from a very large expression

Suppose I have a very long expression (>500,000 characters) which contains a mixture of real and imaginary terms. e.g ...
1
vote
1answer
44 views

Cell seems to be evaluating in exponential time even though it shouldn't

I am trying to implement Newton's method for a given function f[x] and a starting x-value xval. The code should print out each new x-value as it approaches one of the zeroes of the functions. g[x] is ...
1
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2answers
405 views

Converting expression into string without evaluating it

How can one convert a Mathematica expression into a string without the expression being evaluated first? I tried using Hold, but it returns ...
1
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1answer
133 views
1
vote
1answer
5k views

Evaluate an expression at a specific point

In Maple, you right click and can evaluate an expression (whatever it is) at a specific point say: Expr.= abcddafjosjfoj, then right click and simply evaluate at c=-34 say. But how does one do the ...
1
vote
1answer
169 views

direct assignment to the element in a Table

I have already asked a related question here why set values in this way doesn't work? But I think I have to write the question which I encountered explicitly? ...
1
vote
1answer
42 views

How to get Mathematica to abort the current evaluation if an assertion fails?

I can turn on assertions, but they don't terminate the current evaluation. For example: ...
1
vote
1answer
47 views

GCD of Table entries

This question is from a newbie, so please be gentle in thrashing if I'm missing something very basic. How can I use GCD on a matrix/vector entries stored as Table. For example, if ...