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
82 views

Need to run evaluation 2 times

Why does this only work after running the evaluation 2 times? ...
2
votes
1answer
240 views

Expectation function does evaluate my expression

I am trying to evaluate the expression Expectation[(B x (-6 b + 12 a n0 + B x + B^2 x^2))/(2 (6 a + B x + B^2 x^2)), Distributed[x, BetaDistribution[α, β]]] ...
2
votes
1answer
4k views

setting a variable equal to the output of FindRoot

So I set a function f[x] f[x_] := x*E^(-x) - 0.16064 Then I set a variable 'actualroot' to the function FindRoot, starting at 3 ...
2
votes
1answer
112 views

Nested If statement with unevaluated arguments

I have a list of boolean functions {f1, f2, f3, ...} that take a value and return True or ...
2
votes
1answer
111 views

Mathematica displays the unevaluated expression Expectation function

The evaluation runs for a few seconds and then Mathematica displays the unevaluated expression Expectation function ...
2
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1answer
109 views

ParallelEvaluate: Evaluation Rules and Increment

I'm trying to understand how ParallelEvaluate works, considering the two following snippets: ...
2
votes
1answer
88 views

Defer parts of the expression

Is there a way to Defer only parts of the expression? For example, I have a=1; and then I want the expression to be shown as...
2
votes
1answer
185 views

Wrapping at evaluation for inline cell

I've been playing with inline evaluation and I've came to the conclusion that it's most convenient to put the Dynamic@ inside the inline cell, so I've started to ...
2
votes
1answer
110 views

Manual CellGrouping option causes crash at cell evaluation

Update: Try to reproduce this behaviour with CellGrouping set to manual. To do that: either evaluate ...
2
votes
1answer
254 views

Why is this expression being held, and how can I evaluate it?

I can't figure out why an expression isn't evaluating, even though there's no Hold* in its FullForm: ...
2
votes
1answer
254 views

Manipulate executes expressions multiple times

I am using Manipulate for a rather intricate front end for data visualization. I was getting very sluggish performance and was able to boil the problem down to a ...
2
votes
1answer
339 views

Evaluate Numerator and Denominator Separately

I have this function. ...
2
votes
3answers
155 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 ...
2
votes
2answers
91 views

How can I partially evaluate a function?

I have a multivariable function, from which I'd like to define a marginalization: f(a,b,c,d,...,z) ---> g(a,1,c,d,...,z) Generally, g will have fewer argument than f, possibly none (full ...
2
votes
2answers
80 views

How to apply list of values to a list of functions

I have the following: first= {1+a,2+a,3+a,4+a} and a list t={0,1,2,3} I want to evaluate the first element of "first" at ...
2
votes
1answer
48 views

Is there a simple function identify the sign of an expression given constraints

I'm looking to find a simple function that can identify the sign of an expression given a set of constraints. I have looked around and do see that there is a few threads on this but I'm not sure I ...
2
votes
1answer
105 views

How to explain the behavior of Rule inside these functions [duplicate]

I'm trying to define a function that takes an expression and spits out a pure function involving a replacement rule of that function's variable. An example would be a function ...
2
votes
1answer
207 views

Confused about Unevaluated

Why does Map[Unevaluated, Table[PauliMatrix[i], {i, 1, 3}] give {Unevaluated[{{0, 1}, {1, 0}}], Unevaluated[{{0, -I}, {I, 0}}], Unevaluated[{{1, 0}, {0, ...
2
votes
3answers
432 views

GraphPlot only working when I evaluate twice

I have some code that builds a graph and some vertex coordinates, but when I evaluate it I get a message that the list of coordinates is not valid and the graph is not valid and it shows the output as ...
2
votes
3answers
53 views

Display a part of a notebook when MMA has done evaluating it

When you evaluate a notebook, it begins to slide upward and shows you a different part of your code, several cells upstream of the notebook... I was wondering if there is a command that could always ...
2
votes
1answer
77 views

How can I set a RadioButton to invoke an action, like a Button can?

In Mathematica one can create a Button which, when clicked, invokes an action. For example... ...
2
votes
1answer
66 views

Inactive derivative: extract constants

I have a problem with an unevaluated derivative. In the example code below, i need the integration wrt to y be evaluated, while the differentation wrt x needs to stay unevaluated. I see the point that ...
2
votes
2answers
73 views

Order of Evaluate for Map

I would like to get a list of variable names as strings. For example, x = 1; y = 2; Map[SymbolName, Unevaluated /@ Unevaluated@{x, y}] {"x", "y"} This works ...
2
votes
1answer
130 views

Generate conditions seems to not work [closed]

I am trying to compute the following integral Integrate[E^(I*k*Omega*t), {t,0,T}, GenerateConditions->True] for which Mathematica returns ...
2
votes
2answers
78 views

Can I have Mathematica show intermediate forms before final evaluation?

If I have x = 2 and I want to evaluate y = x^2 I would like to the output to show ...
2
votes
1answer
41 views

is there a way to construct a pattern that would trigger when an expression is used as a held/unevaluated in some form?

For example, consider the following code f[x_] := (Print["evaluated f"]; workWith[x]); We use it, then f evaluates: ...
2
votes
2answers
1k views

Integrating a Simple Piecewise Function

If I define f[x_]:=If[x<0,-1,1] and then integrate,say Integrate[f[x],{x,-3,7}] I get what I expect, namely 4. But ...
2
votes
1answer
104 views

How to extract a variable names (not values) from a list of transformation rules?

I am trying to extract variable names from a list of transformation rules mapping = {var1 -> 'val1', var2 -> 'val2' }. Variables ...
2
votes
2answers
188 views

Generating an editable table that can be used as input

Say I have a number $n_{max}$. I want a command to generate a table like 1 1 2 2 3 3 4 4 ... nmax nmax where the second column is editable, and this table can be ...
2
votes
1answer
138 views

Need help looping a notebook evaluation

I'm a new user and would like to find the minimum value of soln1[30] obtained after repeating the following evaluation (below) for 1000 cycles (for instance). I can obtain sequential values of ...
2
votes
1answer
124 views

Differentiating a function that has NIntegrate within it

I am something of a novice with Mathematica. I have written the following code; ...
2
votes
1answer
166 views

Evaluation of the second argument to NIntegrate

The expression Integrate[x^2, Flatten[{{x},{1,2}}]] evaluates properly, to $\frac{7}{3}$. However, ...
2
votes
1answer
58 views

Label cell goes away with SelectionEvaluate

When a given cell has a label (given with the CellLabel->"label" option of the cell), then this label disappears after calling SelectionEvaluate[ nb ] when the ...
2
votes
1answer
261 views

Dynamic [ NotebookEvaluate [“_”] ]

A nice way to centralize various tasks in one notebook is the NotebookEvaluation function. For instance I can evaluate ten notebooks from a single notebook (e.g. ...
2
votes
1answer
139 views

Reuse local variable in declaration within With [duplicate]

Considering the richness of Mathematica.SE, I am quite surprised I could not find my answer... I am very sorry if it is a duplicate. Consider the following example: ...
2
votes
1answer
131 views

NotebookWrite undo

Is there way to make NotebookWrites undooable? For example let's say I open a new notebook and then run. ...
2
votes
1answer
47 views

Non-autonomous Dynamical system Sliding mode controller Error

This code is a simulation of a sliding mode controller of a non-autonomous dynamic. When I use ArcTan in input, I receive an error. ...
2
votes
1answer
63 views

Failure in the use of FullSimplify

My question is about an apparent failure of the function "FullSimplify" to simplify an easy algebraic expression. This is the expression that I ask Mathematica to evaluate: ...
2
votes
1answer
60 views

Why isn't Table iterator value inserted in failed NIntegrate arguments?

Consider this simplest example: Table[{z, NIntegrate[f[x], {x, 0, z}]}, {z, {1}}] Here f is not defined, so ...
2
votes
1answer
99 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
287 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
100 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
692 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
164 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
23 views

SelectionEvaluate executes out of turn

I'm seeing some unexpected (to me) behavior from SelectionEvaluate. I've got a notebook with two sections. In section 2, I've got code that clears the notebook's ...
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
61 views

What is the difference between GenerateDocument and TemplateApply[NotebookTemplate[

Abstract GenerateDocument[ _NotebookObject ] seems to do the same what TemplateApply[ NotebookTemplate @ _NotebookObject ] ...
2
votes
0answers
167 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 ...