Questions tagged [evaluation]
Questions about how Mathematica evaluates expressions, tracing evaluation (Trace*), handling expressions in unevaluated form (Hold*, Unevaluated), nonstandard evaluation, etc.
1,169
questions
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0answers
31 views
Are Hold attributes Mathematica's way to implement lazy pattern matching alla Haskell?
I'm reading this and I'm having a hard time understanding lazy patterns; in particular I'm baffled with the server-client toy problem and why there is a 'problem' of matching "...too early".
The ...
2
votes
1answer
66 views
Using chain rule to calculate a second-order partial derivative in spherical polar co-ordinates
I have a function $f$ and I am supposed to calculate its second-order partial derivative first in cartesian co-ordinates, which is fine. However, I am stuck while solving the problem in spherical ...
0
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0answers
35 views
Radial Mathieu functions, divergence problem
I am working on a project that requires the utilization of even Mathieu functions.
This is the definition of my functions:
Even Mathieu function: ...
0
votes
0answers
43 views
Odd ordering of evaluation for piece-wise functions, element-wise multiplication and dot product
I am constructing functions that call on multiple other functions and I want to understand how the ordering of evaluation of functions works and what is the best practice when writing many component ...
0
votes
1answer
53 views
Defining relations between functions in Mathematica
I would like to find a way to implement the following in Mathematica:
Let $F$ be the set of real functions $f_1,f_2,\ldots f_n$. The function $\min$ is defined as follows...
$$\min F=f_i\iff \forall ...
1
vote
1answer
38 views
Insert result of inline evaluation [closed]
In previous versions of Mathematica I could inline evaluate the call to Solve in the code below with the result replacing the call. Very useful to speed code up.
...
1
vote
2answers
24 views
Assign numerical values to symbolic variables in a vector inside a do loop
I have vector k = {k1, k2, k3, k4, k5, k6}.
I would like to assign numerical values to the elements of k in each step of a <...
2
votes
1answer
55 views
any way to stop all the following evaluations?
I often slect the whole notebook to evaluate. Sometimes some functions may return wrong parameters, which may happen, for example, I may have forgotten to specify values to some variables in the ...
0
votes
3answers
52 views
Partial evaluation of a function [duplicate]
In the spirit of a previous question, this is a self-assigned exercise in order to understand how we can control expression evaluation with Mathematica.
So, given the following function definition:
<...
0
votes
1answer
51 views
Retrieving the evaluation result of an Initialization Cell in a notebook `nb1` from another notebook `nb2`
I have a very long code in a notebook nb1 in which all the initialization cells are tagged. I have another notebook nb2 where I ...
0
votes
1answer
59 views
Through does not have hold attribute?
Possibly Related to Unexpected behavior of KeyTake.
Consider the following example, where I input #11 (last) is the misbehaving one. Am I missing something or do you agree there is a bug?
...
1
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0answers
31 views
Changing machine precision notebook-wide leads to peculiarities
For a project of mine it is preferrable to set notebook precision globally. I have done so by using the answer in Global precision setting.
The idea is to dynamically create a ...
7
votes
1answer
110 views
Accessing sowed data during long computation
This question is very similar to the one posted here: Interrogating a running evaluation but my running computation consists of a backtracking procedure which sows valid solutions. It is hard to tell ...
2
votes
2answers
91 views
Manipulate and ParametricNDSolve
EDIT: typo spotted in comments, code reposted with fix as well as new behavior
I'm having trouble getting mathematica to give me a working plot. I've defined specific values for my parameters:
...
4
votes
2answers
96 views
How to extract parts of an expression using Cases
Let the following exprs stand for a list of complicated expressions which we are interested in breaking down into parts by extracting a number of individual ...
3
votes
0answers
65 views
How to plot function with pattern-matched argument and catch-all definition that throws
Consider the following function:
f[n_?NumericQ] := n;
f[args___] := Throw[{args}];
Then try to plot it:
...
1
vote
1answer
26 views
Substitution in delayed evaluation function [duplicate]
I am trying to do the the following: precomputing an expression and then making a function out of it. It has to be delayed evalution, because some of the parameters are only known when the function is ...
0
votes
1answer
51 views
Power towers Power towers from x to n [closed]
How can I make Mathematica calculate a power tower for a succession of numbers, but instead of writing them, Mathematica does the iterative calculation.
...
0
votes
1answer
34 views
Order of evaluation of variable
I'd like to control the order of evaluation in a multi-variable function.
Example: Suppose I have the function:
B[x_, y_] := x + y/x;
If I try to evaluate ...
2
votes
1answer
67 views
Problem with numerical evaluation of a Hankel identity
There an identity with the Hankel functions of both types (https://dlmf.nist.gov/10.11 eq. 10.11.4 or http://apps.nrbook.com/bateman/Vol2.pdf pg. 80 eq. 43):
$$
\sin\left(\nu\pi\right){H^{(2)}_{\nu}}\...
4
votes
0answers
45 views
Run computation in separate process and kill it after a time limit
I am looking for a solution to run a Mathematica calculation in a separate process (separate kernel) and cancel the computation after a given time. If it cannot be cancelled, then just kill that ...
0
votes
1answer
29 views
Testing Expression over region of values
I'd like to test whether this expression is negative when a and b are constrained to lie within (0,1) interval. Any ideas how?
...
0
votes
2answers
86 views
Only evaluate assignments in a notebook
Maybe I'm not using the best programming practices in Mathematica, but my notebooks usually contain a mixture of "definitions" and "computations" with these definitions. Say,
...
0
votes
2answers
30 views
Plotting 3-d function using Evaluate and Table
I want to plot $z(F, x, \lambda)$ where I fix a few values of $F$ and $\lambda$ and see how it varies with $x$. With 2-d functions, I could vary the second parameter easily using a combination of <...
3
votes
1answer
35 views
Prevent argument substitution in held expression when injecting into unevaluated code
I want to write a custom sow/reap pair to wrap any piece of code in sow[code] and call reap ...
0
votes
1answer
31 views
How to have NonlinearModelFit not evaluate a function too early?
This is a follow up of my previous question How can I define the following function for arbitray values of the arguments? that received no attention so here I will try to be more concise with the ...
0
votes
0answers
47 views
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0answers
44 views
InverseLaplaceTransform does not evaluate [closed]
I am very new to Mathematica and not a mathematician, so the question may be very trivial.
I am trying to find the function $f(t)$ such that
$\qquad e^{-e^{s}} = \int_0^{+\infty} e^{-st}f(t)dt$,
...
1
vote
0answers
36 views
How to speed up the evaluation of a sum of incomplete Gamma functions?
We need to do a ContourPlot for the following function $H[x,y,n]$:
...
3
votes
1answer
116 views
An alternative to (%%…%) (k times) [closed]
Sometimes it may be useful to use (%%…%) (k times) to get the kth previous result in a notebook instead of setting a variable.
However, if I want to get the 8th previous result, for example, I would ...
0
votes
1answer
50 views
Getting unexpected results form If expressions [closed]
I'm mystified by this:
g[a_, b_, c_] :=
Module[{d},
d = If[(b < 1), b, b + 1];
If[a < b, d = 0.];
d*c]
g[a, 20, 40]
...
11
votes
1answer
159 views
2
votes
1answer
141 views
Why would Evaluate[] in Plot give me warning about precision?
I have a code:-
Plot[Evaluate@PDF[NormalDistribution[1.6, 0.2], x], {x, -6, 6}]
And then I got the warning: ...
3
votes
2answers
84 views
Construct a function that maps strings to functions
The main question is the last 5 lines (including codes) of this article.
A[x_, y_] := Evaluate[ToExpression["x^2+y^2"]]
A[3,4]
Then the output becomes
...
1
vote
1answer
61 views
How to get ReplaceAll to happen before function call
I have a problem I am attempting to solve with NMinimize.
I have a scoring function, which will give me a final score. The problem has many variables, so instead of having them as parameters, they ...
0
votes
2answers
48 views
Using MinValue with NDSolve
A simplified example looks like this. The basic idea is to maximize fHelper by adjusting \[Alpha] for each ...
0
votes
1answer
79 views
How can I define the following function for arbitray values of the arguments?
Consider the following function
a[m_, l_] = 1/Log[m/l];
with this function I define
...
0
votes
0answers
59 views
Mathematica does not evaluate large expression
I want to apply Conjugate[] to a certain quite long rational function of some parameters. My problem is that although it evaluates perfectly fine on each single part of the expression, Mathematica ...
2
votes
1answer
31 views
How can I keep the argument of TeXForm[Integrate[1/Sqrt[1 + x], x]] from being evaluated?
How can I keep the argument of TeXForm[Integrate[1/Sqrt[1 + x], x]] from being evaluated?
This is what I am getting:
...
1
vote
1answer
35 views
How to interpret a string as a multiline cell of expressions
I need a string like the following:
"2+2
\"Hello
world\"
3+3"
to be evaluate like
2+2
"Hello
world"
3+3
Note that ...
0
votes
1answer
35 views
Unable to operate on the table imported from .mx file
I saved a table by exporting it to .mx file. Now, when I import it back, it gives me the desired output. So, to work with elements of the table, I first define the imported table as (res2 = Import["...
14
votes
3answers
282 views
Evaluated vs. unevaluated Association
This question might have a remote connection to my older question, it is also about sameness of expressions and subtle differences observable only in certain forms.
I encountered this strange ...
8
votes
2answers
161 views
Using `With[…]` with a list specification as a variable [duplicate]
If you have some defined function, say f[a_, b_ c_, x], one can initialize this by using With[...] as
...
1
vote
2answers
58 views
Why does sol[r][[1]] become r?
This is a follow up to this question. This answer is great it gives the correct solution and I can plot it, but I have a problem: when I try to integrate the solution in this way:
...
2
votes
2answers
86 views
InterpretationBox problem with symbolic expressions
Related to this question,
Why does this InterpretationBox construct work when x, y are ...
4
votes
1answer
47 views
Evaluate calls my function multiple times when the function generates an error
If I execute a line of code with Evaluate I find some unexpected behavior when the code returns an error. Here is a minimal example. Let ...
3
votes
1answer
60 views
Combining `With`, `If` and SetDelayed
I just noticed that
With[{x = 1}, If[x == 0, 0, 1]]
returns 1 (as I expected) but
...
3
votes
1answer
117 views
function evaluation - I don't get it
this function returns Pi/4 for a[1,4]
In[...]:= a[r_, n_] :=
Module[{an = Pi/n, h = r Cos[an], w = 2 r Sin[an]}, an];
a[1, 4]
Out[...]= Pi/4
so the kernel ...
6
votes
1answer
105 views
Suppressing analytical evaluation in NDSolve
I am trying to find a numerical solution to a set of coupled ODEs with NDSolve. Let us say $\boldsymbol{X}$ is a vector, and $\boldsymbol{F}$ is a non-linear vector ...
0
votes
0answers
69 views
How to see/trace Manipulate steps?
I am relatively new in Wolfram Language. What I want to solve is tracing "manipulate" steps in one of the demonstration project example codes. In my particular example, there are nearly 20 user build ...
