Questions tagged [replacement]
The replacement tag has no usage guidance.
1,635
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Replacing 2D Patterns in 2D Lists | Markov Programming Language
Recently I came across with a probabilistic programming language where programs are combinations of rewrite rules - Markov Junior
I think it is quite interesting to try out implementing some features ...
- 1,245
2
votes
2
answers
215
views
How to get this nesting working?
I want to nest each element inside the previous at the mid point. How can I do this by indexing a very large list?
...
- 2,360
1
vote
1
answer
54
views
Using Replace with
I have an expression
expr=Derivative[1][A][\[Zeta]] + Derivative[2][A][\[Zeta]] +
Derivative[3][A][\[Zeta]] + Derivative[4][A][\[Zeta]]
I want to replace ...
- 367
2
votes
1
answer
87
views
Pull out numerical factors from the argument
I'm trying to define a function that is distributive over Plus and pulls out the numerical factors from the argument:
...
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2
votes
2
answers
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ReplaceAll for expressions involving negative power [closed]
I have an expression:
$exp=1+\frac{1}{x}+\frac{2}{x^{2}}-\frac{3}{x^{3}}$
I am trying to make the following replacement:
$\frac{1}{x^{i}}\rightarrow f(i)$, where f is any arbitrary function.
The ...
- 23
1
vote
1
answer
109
views
Expression substitution
I konw:
$$
a_0=\frac{4 \pi \epsilon_0 \hbar^2}{m_e e^2}
$$
and
$$
\alpha = \frac{m_{\mathrm{e}}^2 e^4}{18 \pi^3 \epsilon_0^2 \hbar^4}
$$
So we can use $a_0$ for $\alpha$,like this:
$$
\alpha=\frac{m_{\...
- 1,562
1
vote
1
answer
64
views
Function f[a__][b__] with double inputs and definitions/automatic rules
I have a function of the form f[a___][b___] which I would like to apply rules to, for example:
...
- 747
6
votes
1
answer
139
views
0
votes
1
answer
74
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How to replace Indeterminate with NaN in a list and ignore it?
Say I have a list of values and one returns Indeterminate. Is there a way to replace it with say NaN and then keep the rest of the list?
- 103
3
votes
3
answers
189
views
Replacement Rules for names of functions
I don't have much experience in Mathematica and think that my question is pretty straightforward. I have a couple of functions
f1[x1,x2,...],...,fN[x1,x2,...].
For the sake of clarity in the final ...
- 91
0
votes
0
answers
55
views
Solving differential equation using substituion [duplicate]
I've been trying to solve an differential equation using substitution.
I have the equation
...
- 738
0
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0
answers
91
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Mathematica parses `Log[a,b]` as `Log[b]/Log[a]` automatically, before any rules
I use the following code to realize quaternions (this allows more flexibility than the quaternions package):
...
- 3,585
7
votes
7
answers
480
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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 ...
- 73
10
votes
6
answers
719
views
In a list, how to pick whatever is not f and its derivatives?
Suppose I have a list like:
list1 = {{f[x], Sin[x]}, {f'[x]}, {f''[x]}};
list2 = {{f[x]}, {Cos[x], f''[x]}};
I want to pick these lists and convert them to:
...
- 5,329
5
votes
2
answers
234
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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 ...
- 1,667
4
votes
1
answer
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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 ...
- 3,003
1
vote
0
answers
38
views
Simplifying symbolic sums using KroneckerDelta
I am trying to use Mathematica to simplify a symbolic expression of the following form
$$ S_i = \sum_{n_1 = 0}^\infty \sum_{n_2 = 0}^\infty \ldots \sum_{n_M=0}^\infty n_i \times \Big(
\sum_{j = 1}^...
- 231
3
votes
1
answer
79
views
Use two derivative rules and iterate several times to get the simplest expression of higher derivative
I have 2 rules of recursive relation of the derivative, I want to use it several times get the higher derivative on [\Theta] of ...
- 39
9
votes
6
answers
575
views
Replacing integers at level 1 in a list with sequences of zeros
I have a list like this:
l={{2,3},1,{4,7,2,1},3,{2,2,3,3},0,{4,4,2,1},4}
and I want to replace the natural numbers outside the sublists (at level 1) with an equal ...
- 535
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6
answers
434
views
5
votes
3
answers
146
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Substituting the element of a list into a list that contains the index position
I see similar questions for lists and indexes and manipulating with Thread, MapIndexed,etc., but I do not see how to do a substitution.
I have a list of coordinates for a geometric object and a list ...
- 55
2
votes
0
answers
32
views
Replacement rule evaluates before substitution [closed]
I have found similar issues in other questions, but none of the answers I found quite do what I want.
I have a list of the form
list={{x, a}, {y, b}, {z,c}}
and ...
- 131
1
vote
1
answer
59
views
Variable replacement not working in ParallelTable
The following code produces different results using Table and ParallelTable. K and ...
- 4,728
2
votes
1
answer
83
views
Distribute function over one argument
I have a function (say $f$) which takes two arguments. The first argument will either be an integer or a linear combination of f's, and the second argument will always be an integer. If we do have the ...
- 137
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votes
6
answers
599
views
How to replace selected elements of a list of rules with another unbalanced list of rules
I have two lists of rules:
...
- 6,203
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votes
0
answers
49
views
Simplifying expresion with Defer and derivatives
I would like to simplify a complicated expression that contains some derivatives whose evaluation is halted with Defer, using some custom simplification rules. For ...
- 255
2
votes
1
answer
74
views
Rule for derivative of an unknown function
I am taking the derivative of a function with respect to another function, e.g.
D[g[f[x,y]],f[x,y]]
This outputs g'(f(x,y)), as ...
- 747
1
vote
2
answers
68
views
How to perform item shifting deformation?
How to subtract the two equations. That is, the left subtraction of the two equations is equal to the right subtraction of the equation
Continue to the previous question, how to perform the term shift ...
- 4,061
0
votes
0
answers
33
views
How do I prevent, or get rid of the <code>Abs^\[Prime]</code> in the output of a partial of a Normalize[vector]? 12.0.0 for Microsoft Windows [duplicate]
12.0.0 for Microsoft Windows
How do I prevent, or get rid of the Abs^[Prime] in the output of a partial of a Normalize[vector]?
The code below shows the problematic ...
- 1,457
5
votes
5
answers
423
views
How to subtract these two equations?
There are two equations:
eq1 = x1^2/a^2 + y1^2/b^2 == 1;
eq2 = x2^2/a^2 + y2^2/b^2 == 1;
How to get this result by subtracting two equations?
the result
...
- 4,061
7
votes
1
answer
228
views
Ordering Arguments of Antisymmetric Functions in Cyclic Way
I have two functions ang and sqa, each of which take two arguments which must be distinct integers between 1 and 6. For instance I could have ang[2,1] or ...
- 137
1
vote
1
answer
113
views
Operating on specific case given a general case match
I have an expression a which include parts of the form A[i,j], where i,j take a range of ...
- 131
2
votes
0
answers
72
views
how to understand the locality of variables in Mathematica
(in the first i should say may be the title is not very accurate)
how to understand case like the following:
...
- 353
5
votes
3
answers
353
views
Speed up replacement of very large alternatives expression
I'm doing a computation which effectively has the same issue as this code:
Range@1000000 /. (Alternatives@@RandomSample[Range@1000000,500000]) -> 0
i.e. ...
- 3,947
4
votes
4
answers
189
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 <...
2
votes
4
answers
162
views
How to implement replacement rule for products of variables?
If I have an expression in terms of multiplications of (pairs of) variables, e.g. $x_1$ ... $x_N$ such that the expression I want to manipulate is of the form
$A_{1,1}x_1^2+A_{1,2}x_1x_2+\ldots + A_{N,...
- 166
2
votes
1
answer
144
views
How to replace Divide in an expression?
It seems that a/b is always replaced with the form: a * b^-1, Times[a, Power[b, -1]]. I ...
0
votes
1
answer
78
views
6
votes
2
answers
365
views
Defining functions vs using replacement rules
To my knowledge, there are (at least) two ways in which we use functions. The first one is by defining a function
In[1]:= f[x_] := x^2
In[2]:= f[2]
Out[2]= 4
But ...
- 243
1
vote
1
answer
75
views
How to distinguish x[a] from x in replacement rules? [closed]
Quick to the point:is there a way to make Mathematica assume that $a \neq a[1] \neq a[2] , ...$ I notice that Solve assumes that $a$ is the same for all $a[1],a[2],...$ Also, if I replace $a \...
- 95
0
votes
0
answers
35
views
Resetting rules for non comutative multiply
Im currently working on a project that intends to achieve multiple task the first if which rewrite a bra-ket notated triplet tensor product state such as the w state in terms of the pauli matrices.
i,...
- 11
2
votes
2
answers
230
views
How to implement Newton's Identities
I need to produce identities related to Newton's Identities of arbitrary order. More specifically, I need the identities in the following image for an arbitrary n:
What I can't quite wrap my head ...
- 1,526
4
votes
3
answers
183
views
Rule can not work? [duplicate]
For example I have this equation,I want to use c->a/b ,but it can not work
$$
\frac{a^2}{b^2}+\frac{b^2}{a^2}+\frac{a}{b}+e^{a/b}+\frac{b}{a}+\log \left(\frac{a}{b}\right)
$$
...
- 1,562
2
votes
0
answers
92
views
Don't simplify integer square roots
How can I rewrite an expression like $\frac{1}{2\sqrt{3}}$ as $\frac{1}{\sqrt{12}}$?
This works in principle, but gets immediately simplified back to the original expression
...
- 1,419
1
vote
0
answers
56
views
Replace original function inside its derivative
I'm trying to simplify a derivative calculation. I have the Zhs in function of x :
...
2
votes
2
answers
130
views
How can I change variables, if the variables I want to change to are not directly stated in the term?
So I don't mean something like this
f[x_] = x^2
f[x] /. x^2 -> y
But what I mean is something like this:
where the variables I want to change to are defined ...
- 177
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0
answers
36
views
How to pass styles arguments to Style from a wrapper function's argument?
The user-defined symbol styx works fine for style argument values of Automatic and ...
- 2,457
0
votes
1
answer
59
views
How to write a Replace Rule that will Iconize all Rules in a List whose rhs are long String-s?
First, let me illustrate what I'm trying to do. FormatOptions is a programming utility that will Echo a given ...
- 2,457
2
votes
1
answer
51
views
DateObject was not the same as it in the ReplaceAll [closed]
When I use ReplaceAll to replace date objects, I find there will be an error which wouldn't appear when not in the ReplaceAll ...
- 567
6
votes
1
answer
232
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