Questions tagged [evaluation]
Questions about how Mathematica evaluates expressions, tracing evaluation (Trace*), handling expressions in unevaluated form (Hold*, Unevaluated), nonstandard evaluation, etc.
1,501
questions
6
votes
1
answer
92
views
Distinguish three fraction forms (feature stronger than Hold)
This question can not be typed easily, using mathematica stackexchange interface.
So here is a GIF file :
My question is : Can we construct a function f whose ...
- 3,621
2
votes
2
answers
78
views
Don't understand an evaluation with BezierFunction
I don't understand the source of the failure of the following attempts to solve an equation involving the following very simple BezierFunction.
...
- 13k
-1
votes
1
answer
54
views
Calculate the value of an interval [closed]
I want to calculate the maximum value of the formula given in the code, but it is obvious that my writing is incorrect. How should I modify it?
...
- 53
1
vote
1
answer
65
views
Table of conditions seems incorrect
If I enter
Table[Sort@IntegerDigits@x == Sort@IntegerDigits[n x], {n, 2, 6}]
the result is
...
- 4,087
2
votes
0
answers
47
views
Bug: managed library expressions are freed prematurely during evaluation
I believe I have run into a bug with managed library expressions and garbage collection behavior. In the example below, adapted from the documentation for ...
4
votes
3
answers
157
views
HoldForm not working with Map
I am debugging a ListPlot implementation and I need to see the command. To avoid huge list of numbers, i just need the ListPlot ...
- 3,474
3
votes
1
answer
42
views
Strange output of NIntegrate when constraining the precision with $Pre
One can constrain the precision of NIntegrate by setting PrecisionGoal:
...
- 2,754
0
votes
1
answer
79
views
When running code to compute a sequence, loop variable gets set to a constant
I would like to write Mathematica code to read in a list of sequences, and print the sequence definition ($a_n$), along with the sequence evaluated at a few values of $n$.
...
- 1,939
0
votes
1
answer
46
views
Evaluate part inside HoldForm [duplicate]
What I want to do is pretty straight forward: Entere something like this:
HoldForm[Sum[la /. a -> b, {l, 0, N}]]
and get something like this
Σ lb
Generally spoken, holding the sum but evaluating ...
- 3
2
votes
1
answer
49
views
How to modify the argument of a specific function below?
I would like to change the values of a and b in the following function:
...
- 232
0
votes
1
answer
48
views
Can Print no longer access certain values during evaluation? [duplicate]
This example from Power Programming in Mathematica doesn't work for me anymore: the values used for rootfinding are not printed during evaluation. What changed? Is there a new way to reproduce the old ...
- 1,706
3
votes
1
answer
140
views
How to get the closed form solution from DSolve[]?
Hi I've noticed something rather annoying which is when I try to use this function DSolve to check the answers to my homework problems it will simply not show a solution due to lazy evaluation.
E.g.:
<...
- 133
3
votes
2
answers
57
views
Convert Strings in Variables [duplicate]
I want to convert strings to variables. I want to create the term pionprodg1. I tried to do this:
...
- 153
6
votes
6
answers
453
views
How do I withdraw the rhs from a list of equations?
I have a list of equations that were solved for different values of another parameter and stored in a Table and has the form:
{a==0, a==1, a==2, a==3}
and so on. I ...
- 63
5
votes
2
answers
203
views
Do not understand evaluation order of ReplaceAll [duplicate]
{x, x^2, Length@x, Subsets[x]} /. x -> {1, 2, 3}
(* {{1, 2, 3}, {1, 4, 9}, 0, {{}, {1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, {1, 2, 3}}} *)
with error
What ...
- 817
4
votes
1
answer
153
views
RuleDelayed (:>) involving Piecewise leads to Piecewise::pairs warning in ReplaceAll (/.)
When I write a replacement rule like this:
Piecewise[{{x^2, x < 0}}] /. Piecewise[a_, b___] :> Piecewise[a, b]
It works fine, but I get the unexpected ...
- 2,923
1
vote
1
answer
52
views
Plus[__] matches everything in MatchQ [duplicate]
I understand that
Clear[a,b,c]
MatchQ[a+b+c, Plus[__]]
True
Because a+b+c is in fact ...
- 3,621
7
votes
2
answers
165
views
Map function with evaluated and unevaluated parameters
Let's consider a function with evaluated and unevaluated arguments inside:
list1 = {1,2,3}
list2 = {x,y,z}
fun[list_]:={list,ToString@Unevaluated@list}
When I use ...
- 225
3
votes
3
answers
180
views
Building A Function Using Constants From a List
I want to build a function of the form
$f(t)= C + \sum_i A_i*Sin(f_i*t+\phi_i)$
Where $(A_i,f_i,\phi_i)$ are amplitudes, frequencies and phases that I have stored in a text file. Here is my attempt:
<...
- 43
4
votes
1
answer
59
views
another problem with context using package and association when using Inactivate
This problem is similar to this problem using package to verify solution of ode with Association, Naming scope/context handling but when I used the solution/trick given there, I still get a problem.
I ...
- 127k
4
votes
3
answers
110
views
How to evaluate EXPR in a subsession of a different already running kernel and get the output?
Is there a way to evaluate some expression in a subsession of another already running kernel, collecting the output, from a Local monitoring kernel? Something like
...
0
votes
0
answers
62
views
Answer changes slightly when re-run
I am trying to resolve why I get slightly different answers when I re-run my notebook. Here is my full code:
...
- 1
2
votes
1
answer
47
views
Aborting the loop using external events
If we run one Wolfram Kernel (Wolfram Engine) there is one thread we can use
While[True,
doSmth;
Pause[0.1];
];
since there is a sort of interruption ...
- 597
0
votes
1
answer
62
views
Compute all bivariate polynomials over GF(2) of degree d or less and evaluate them at certain polynomial input
I want to compute all $<=d$ degree bivariate polynomials of form $f_1(x)g_1(y) + f_2(x)g_2(y)$, over field $GF(2)$, and evaluate them at a certain polynomial input
for eg $d = 1$, evaluation at $(p^...
- 1
4
votes
1
answer
153
views
Why is Evaluate[] in Plot[] not necessary in some cases?
after reading some related materials(Why do I have to put Evaluate[] here), in my understanding, BecauseAttributes[Plot] has ...
- 147
0
votes
0
answers
45
views
MMa 13, holding previous solutions instead of clearing them
I suspect this is something one line of code will fix, but I have a fairly simple code, that needs to be evaluated at 2 different points. I tried it for the first one... got an answer, it's correct, ...
- 505
1
vote
2
answers
84
views
Construct association depending on itself
I want to construct an association that some of the Values are constructed from other parts of the Values, for the simplest ...
- 1,440
0
votes
0
answers
39
views
Some confusions about Evaluate[] and HoldAll in Plot[] [duplicate]
i can't understand the outputs of the three commands in the following picture.
question1:
In my understanding, command one Plot[Table[a*x^2,{a,3}],{x,-3,3}] is ...
- 147
4
votes
4
answers
164
views
How to use replacement rules in a named expression before a sub-expression evaluates?
I have a named expression: expr := a + b. a and b are also named expressions.
Let's say <...
0
votes
1
answer
53
views
What is the proper way to use Manipulate and Graphics in this context?
So this is my setup: I want to have an unspecified number of points, let's say n, which I can manipulate in a Manipulate environment. I want to later use these ...
0
votes
1
answer
63
views
Problem with For Loop when evaluating a recursive function at multiple points
I am running into problems with my For loop when trying to evaluate my expression. Fix some parameter values :
...
- 3
0
votes
0
answers
66
views
Map-ed programmatic Style-s (based on user-input) are not evaluating. Scoping constructs are suspected
The top function manages several sub-functions which set visual properties over a list of Options.
Inside stylerules the ...
- 2,337
0
votes
0
answers
42
views
Preventing Evaluation of Body of Manipulate
Overall, I am looking for a way to prevent the evaluation of the body of Manipulate until the controls meet a certain condition.
For example, consider the following....
- 1,587
4
votes
0
answers
68
views
Why does `MakeBoxes` have the HoldAllComplete attribute and ignore it rather than HoldAll?
MakeBoxes has the attribute HoldAllComplete. For a normal function, it would imply that Upvalues should not be taken into account when the expression is evaluated:
<...
2
votes
2
answers
178
views
The derivative anomaly in Mathematica 13, showing in the Plot[] function
Edit:
Still inexplicably, it was found that in the Plot[] functions, showing a correct curve plot for the expression computing the derivative incorrectly, when '...
- 313
4
votes
1
answer
127
views
How to evaluate this InverseFunction?
Solving an ODE problem
DSolve[{y'[x] == x*(y[x]^2 - 1)^(2/3), y[1] == 3/2}, y[x], x]
...
- 21.1k
2
votes
1
answer
129
views
Define Conformal Metric in xAct
For my thesis, I'm reproducing the results of a paper here by Alic et al in Mathematica using the package xAct.
I'm able to reproduce the standard $3+1$ ...
- 163
0
votes
1
answer
35
views
Parts of the expression are evaluated well, but not the whole expression together
I have the following code inended to define quaternions:
...
- 3,399
3
votes
4
answers
404
views
Define a delayed function depending on a global variable as though the variable's contents was pasted
Problem
Say I previously defined a variable (maybe through some extensive calculation)
thing = (a+x)y
Then, I want to use that expression elsewhere. In general, I ...
- 689
1
vote
2
answers
103
views
Symbolic manipulations of predefined variables without numerical substitution
As a novice in Mathematica I would like to expand an expression without substituting its variables so that
x = 4; y = 4;
Expand[(x^2 + y^2)/x^2]
generates the same ...
1
vote
2
answers
246
views
How to prevent Mathematica from rounding some PDF values to 0?
Dear Mathematica community,
I'm having a problem with the PDF function for the hypoexponential distribution. Specifically, Mathematica returns 0 as soon as the value is very small. Below is an example:...
- 21
0
votes
0
answers
51
views
Plotting D of Sin fails but ' of Sin does not [duplicate]
I understand why you have to use Evaluate with D to make it work, but why then does the apostrophe form work for Derivate without Evaluate?
If I plot a derivative one way I get an error - and yes, I ...
- 551
0
votes
1
answer
67
views
Cannot plot a function that calls Eigensystem on a large matrix
Is there a way to plot an expensive function without resorting to making a list of values and using ListPlot?
I have a function called ...
- 1,706
5
votes
5
answers
1k
views
How to simplify a pure function?
I am dealing with the vibration of a multi degree of freedom system with driving force, and I need to find the relation between the amplitude and the frequency of the driving force.
I hope to get an ...
- 328
4
votes
1
answer
202
views
Substitution rule is not working
I'm trying to replicate the equations of motion of the $4\partial$ST theory in Mathematica as is done in here as I need to use Mathematica and this package for my thesis. However, I have some trouble ...
- 163
-2
votes
1
answer
149
views
8
votes
4
answers
286
views
How to Thread lists elementwise with the If function?
Consider the lists:
list1={a,b,c};
list2={x,y,z};
I want to Thread If elementwise across ...
- 431
2
votes
2
answers
143
views
'Update' and how to use variables to define patterns in functions' arguments...?
This seems like an obvious issue that I have nevertheless never encountered before.
In a package, I want to use a variable to define a pattern that is used in the definition of some functions. However ...
- 1,407
2
votes
2
answers
99
views
Replacing symbolic variables inside of a compile
As the result of a symbolic integration, I have a very long array with symbolic variables u[i] which I would like to substitute for real number values. Moreover, I ...
- 153
0
votes
1
answer
68
views
Preventing evaluation of $Exp[\pm i\pi]$ until the end of a calculation
I'd like to prevent Mathematica from evaluating $Exp[\pm i\ \pi]$=-1 until I tell it to, at the very end of a calculation. I have a lengthy expression that involves things like (-x+y)^(n), and I know ...
- 1