Questions tagged [evaluation]
Questions about how Mathematica evaluates expressions, tracing evaluation (Trace*), handling expressions in unevaluated form (Hold*, Unevaluated), nonstandard evaluation, etc.
1,426
questions
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Parts of a Piecewise Matrix Function in NDSolve
First time posting.
Reproducing the Problem
I'm relatively new to Mathematica (using v.12.3), and working on a project. My problem can be reproduced with this.
...
6
votes
1
answer
194
views
How to remember evaluation across sessions?
I am performing a very time-consuming symbolic calculation.
When I reopen a saved Mathematica notebook, it takes quite a long time to evaluate.
Is there an option to tell Mathematica to remember the ...
- 61
2
votes
1
answer
52
views
Wierd problem with Table and Evaluate
I have a very unpleasent problem with Mathematica, precisely with Table and/or Evaluate. After solving a parametric system with ParametricNDSolve, I'd like to collect the values of the solutions $f_3(...
1
vote
0
answers
84
views
Why Mathematica don't set \$RecursionLimit and \$IterationLimit very big by default? [closed]
For my current program in Mathematica, sometimes I will encounter an error regarding \$IterationLimit and \$RecursionLimit. So I always set these two numbers to very large at the starting of every ...
- 11
3
votes
3
answers
214
views
Different evaluation control inside of `Integrate` than outside of it
I want to keep inside of a integral evaluated after some replacement inside it, but at the same time the integral itself unevaluated.
I start with:
...
- 2,503
6
votes
3
answers
233
views
HoldForm is not working as I would expect
Why HoldForm do this?
HoldForm[a/b \[Integral]f[x] \[DifferentialD]x]
Output is this ugly looking formula:
$$\frac{a \int f(x) ...
- 2,503
0
votes
0
answers
56
views
Can I load a notebook without evaluating it?
I have a long notebook with a lot of definitions, calculations, etc. If I want to open the notebook on a new computer, or even on my computer after it has been shut down; then in order to make use of ...
- 101
1
vote
0
answers
33
views
How to derive the integral of a first kind zero-order modified Bessel function multiplied by a Rayleigh distribution?
I input the result into Mathematica and get the following result
In: $\int_{0}^{\infty} \operatorname{BesselI}[0, \epsilon] * \frac{\epsilon}{\rho^{2}} * e^{\left(\frac{-\epsilon^{2}}{2 * \rho^{2}}\...
- 11
0
votes
0
answers
51
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Variation with respect to inverse metric in a Lagrangian density
I am trying to vary the following Lagrangian density
with respect to the inverse metric appearing in the equation, but I am having trouble with how to write the right code in Mathematica.
I have ...
- 1
5
votes
4
answers
290
views
How can I efficiently define functions with different names but doing the same stuff?
Recently I have met with with this interesting question:How can I efficiently define functions with different names but doing the same stuff? Somebody may want to ask me why I want to do things like ...
- 289
2
votes
2
answers
143
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Double quotes as a 'function' (verbatim ToString?)
Can we construct a function F such that F makes any typed text into a string.
Just like double quotes.
...
- 2,451
0
votes
1
answer
46
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How to construct the local variables for Block automatically (somewhere in the code)
I am working on the fancy abstraction for Block function. The idea is to use rules to specify which local variable will be used, even if it already defined in the global context
like this
...
- 115
3
votes
3
answers
237
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Seemingly identical expressions, only one evaluates! [closed]
I am having difficulty using NMaximize with a user-defined function that involves NSolve. Stack Trace shows trouble at the ...
- 131
1
vote
3
answers
98
views
How to return unevaluated variable?
I'm not sure if this problem has been asked before as I don't know the keyword to search for it.
I have a function where return result contains variable b (just ...
- 1,750
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0
answers
61
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Why does my function for LocalSubmit successfully create a TaskObject with no errors but ignores my simple Print task?
tldr: for lazy readers (don't blame you im sometimes that way too) or those who found my details below a little bit vague my question is: why is my Print not ...
- 1,787
2
votes
0
answers
45
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Division by 0 Error when checking whether something is equal to zero
I was running a program and suddenly got Divide::infy messages coming from the following (rather ugly) expression.
...
- 928
3
votes
1
answer
43
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Trying to add up values into a matrix
first post here.
I'm currently completely stuck and frustrated with mathematica. In retrospective, it might had been a mistake to use it for this, I'm actually considering to somehow export the ...
- 33
4
votes
3
answers
263
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Expectation of a Sum
I'm using Expectation to calculate the Gaussian integral of a user-supplied function. The following works well and fast (< 1 second):
...
- 17.6k
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0
answers
34
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Define a new rule to take precedence over the others in a symbol's `Downvalues` list [duplicate]
I have a symbol that has a very large list of Downvalues. One of the rules in this list should be applied before the others because it simplifies many expressions, ...
- 1,448
3
votes
1
answer
87
views
how to split indices for a Spinor object?
I am wondering if anybody can help me with my question. My main relation is from gravity and is known as self-dual Riemann. When it is written in the Spinorial form it is like:
$$G_{\mu \nu \alpha\...
- 57
3
votes
1
answer
73
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Replace previous equations into the current one in a recurrence relation
I have a recurrence relation given as follows:
f[k + 1] == 1/a[k, k + 1] Sum[a[k, k - k1] f[k - k1], {k1,0,k-1}]
Evaluating it for ...
6
votes
1
answer
182
views
Getting terms and only evaluate specific parts of a series
How to write the first five terms of this series in the following form by MMA code?
$\sum_{n=1}^{\infty} \frac{1 \cdot 3 \cdot \cdots \cdot(2 n-1)}{2 \cdot 4 \cdot \cdots \cdot 2 n}= \frac{1}{2}+\frac{...
- 1,365
1
vote
1
answer
91
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Evaluating a mathematica notebook via the command line and saving the evaluated file
I am attempting to evaluate a notebook with the following code via the command line
...
- 79
0
votes
1
answer
42
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Multivariate function won't evaluate
When I define the following variables and function and then evaluate that function at given values:
...
0
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0
answers
40
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How to stop annoying notifications sound when using "Remove from Evaluation Queue" shortcut?
I have Mathematica 13.0 Student Edition for Windows 10 and whenever I use " Shift + Alt + / " I get this annoying "Windows" notifications sound. There has to be a way to stop it, ...
0
votes
0
answers
53
views
Logical functions with no arguments
I am trying to understand how logical functions are evaluated if no arguments are passed to them.
{Or[], Nor[], And[], Nand[], Xor[], Xnor[]}
{False, True, True, ...
- 14.8k
3
votes
2
answers
104
views
Integration of differential given as one-form
I would like to use the integration symbol in more general way, that means to integrate any differential, like
\[DifferentialD]y = a x^2 \[DifferentialD]x
and then
<...
- 577
2
votes
1
answer
83
views
Activating part without resolving [[1]]
I'll try to make this question more clear in a little while. In the mean time, I'll ask directly the question which motivated it:
Latin Square from submatrix
Original Question
I want, for instance, ...
- 2,648
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0
answers
40
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How do I make divergent integrals to be automatically evaluated?
As a first step I want the divergent integrals to be evaluated to their Laplace transform, like this:
$\int_0^\infty \sin x dx\to 1$ because ...
- 2,721
1
vote
2
answers
74
views
Theoretical Timing possible? (not changes for each evaluation)
Is there a method to measure theoretic time load (hope +theoretic memory load) of an evaluation?
They should not change - always generate same value after pressing Enter key(=evaluation).
Hope they ...
- 2,451
5
votes
1
answer
241
views
Lazy vs strict evaluation approaches - performance comparison
In general, I think there are two methods of evaluating a variable in Mathematica. My question is about performance of the two methods.
Suppose that our final goal is to evaluate ...
- 2,451
3
votes
1
answer
64
views
Compile function dynamically
To optimize a brute force algorithm on graphs I want to compile dynamically a list of functions for a list of graphs.
(The representation I'm using for a graph is a list of pairs of integers: integers ...
- 461
1
vote
0
answers
66
views
Why does Plot function have HoldAll attribute?
I had an odd issue where my plot wasn't drawn correctly when I called it via Plot[Join[fs,gs], (*..*)]. However, these two versions worked:
...
- 111
0
votes
0
answers
91
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Help with Error: Recursion depth of 1024 exceeded during evaluation
I am quite new to Mathematica. Please excuse my mistakes. I would appreciate if you could help me with the following set of commands.
...
- 1
0
votes
1
answer
71
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How to count Kernel evaluations then call a function on every nth evaluation
On every nth (2) evaluation autoEval should invoke a function check[]. The thing which is supposed to listen for all ...
- 1,787
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vote
1
answer
83
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Smart way to do a numeric integral of a recursive function defined by symbolic integration
I have a little question. I need a smart way to compute a numerical integral.
The standard way to compute a numerical integral, in multiple variables, is, for example, the following:
...
0
votes
1
answer
157
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Numerical integration of a function with Dirac delta
I have a little question about the numerical integration of a function that includes a Dirac delta.
I have the following function:
...
3
votes
0
answers
144
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Using new FoxH function to solve a trinomial equation. Possible issue?
There is a possible issue on solving the following trinomial equation
$$x^\alpha+x=y$$ for real $x,y,\alpha$. From Belkic [1], it is known that for $\alpha>1$ a solution is found using the ...
- 131
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votes
0
answers
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How to convert Graph atomic object back into unevaluated expression? [duplicate]
For the purposes of further development of my shortInputForm function, I wish to convert Atomic objects such as Graph into non-...
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votes
2
answers
36
views
Noncommutative multiplication with rational functions as coefficients
I am considering formal functions of lists and used ** to define the concatination product:
bb /: bb[X_] ** bb[Y_] := be[Join[X, Y]];
So that for example bb[{a,b}]...
3
votes
3
answers
106
views
Apply HoldForm on only a part of an expression
This expression:
Det[Array[a, {3, 3}]]
is evaluated as:
$-a(1,3) a(2,2) a(3,1)+a(1,2) a(2,3) a(3,1)+a(1,3) a(2,1) a(3,2)-a(1,1) a(2,3)a(3,2)-a(1,2) a(2,1) a(3,3)+a(...
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votes
4
answers
159
views
Can I change the meaning of operators? For example ∈ as MemberQ
I spotted this under \[Element] in the Wolfram documentation: "x ∈ y is by default interpreted as ...
- 1,055
5
votes
2
answers
178
views
Table of functions
Why does
Table[Function[{x}, x^m], {m, 1, 3}]
produce
{Function[{x}, x^m], Function[{x}, x^m], Function[{x}, x^m]}
(i.e. with <...
1
vote
0
answers
39
views
What is the difference between "SessionSubmit" and "LocalSubmit" in performance?
Does SessionSubmit forward the computation to the master thread and LocalSubmit to some other idle thread? By thread, I mean CPU ...
- 365
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vote
0
answers
47
views
I want a symbol to be automatically converted to an expression on input but not on output
I want the symbol j to automatically convert to {-1,1} on input, but when seen in output stay intact. What can I do for that?
I ...
- 2,721
3
votes
2
answers
132
views
How to make c[n_, x_, y_] := ToExpression["p" <> ToString[n]] = {x, y} work?
I am trying to do the following:
c[n_, x_, y_] := ToExpression["p" <> ToString[n]] = {x, y}
That is: Evaluating ...
- 4,801
0
votes
1
answer
109
views
Mathematica stuck on partial derivative calculation
I was experimenting polynomial gradient descent on Mathematica, but it got stuck on partial derivative calculation. Formula below:
Traditional Form:
$$
mse = \frac{\sum_{i=1}^{n}\left(y[[i]] - \left(a\...
- 119
3
votes
1
answer
156
views
Plot a double integral
I'm trying to plot the result of a double Integral
Plot[
Integrate[Integrate[x^7 (x - 2)^4 (x - 3)^9, x], x]
,{x, -10, 10}
]
Results in a 22-degree ...
- 389
5
votes
3
answers
278
views
Apply Plus as a new head to a list but prevent evaluation
I would like to illustrate to users the use of Apply with an example.
Plus@@Range[5]
(*15*)
To display what is happening I'm ...
- 1,603
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votes
0
answers
53
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How to evaluate simplify an expression containing derivatives
I have an expression that is a derivative of order 2. I want to assign value to derivatives of orders lower than 2(e.g. the expression itself) which should cause the derivatives of higher order become ...
- 340