Questions tagged [replacement]

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45 views

Testing a condition to replace elements of amatrix

I want to write a code that checks each element of a given matrix C2 and in case they are't 0 or 1 , replaces them with 1. My code is so far as follows and the code ...
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1answer
45 views

Efficiently converting equations into coefficient matrix

I have a list of n linear equations in variables state[i] for i = 1, ..., n and ...
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1answer
66 views

Replace two objects in an expression

So I have a long expression that looks like this: a (e1.e3)^2 (f1.e2)^2 + b (e1.e2)^2 (f1.e3)^2 + c e1.e3 e2.e3 f1.e2 f2.e1 + ... What I want to do is to replace ...
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3answers
279 views

ReplaceAll, Unexpected output

Each week I import a dataset, and every week the dataset differs in length (the number of records). After the import I need to do some transformations. One of these transformations is the ReplaceAll. ...
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0answers
27 views

Remove empty TextCell[] from numerical expression

I am evaluating an expression like this: ...
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1answer
49 views

Define/store individual elements of Table output for back-substitution

At its core, mine is a very simple communication error between me and Mathematica that I haven't been able to crack, so I do apologise if it seems embarassingly inane. Please consider the following ...
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2answers
38 views

Replacing function by another one each time it appears

I have expression involving Cos of some parameters. I would like to replace those Cos by their infinite series each time they do appear. I tried the following which doesn't work: ...
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0answers
22 views

Different results when using ReplaceAll

Here's a riddle. I have a matrix QQsimple with some algebraic expressions. For example: QQsimple[[36, 22]] evaluates to: ...
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2answers
220 views

Given x ⊕ x =5,x ⊕ (y ⊕ z) = (x ⊕ y)+z-5 what is 2009 ⊕ 1949

There is an operation "⊕" that satisfies $x ⊕ x =5$ $x ⊕ (y ⊕ z) = (x ⊕ y)+z-5$ what is 2009 ⊕ 1949? I think it is feasible to solve with Mathematica, but my code doesn't give a useful ...
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1answer
53 views

Change Replace Rule with Function Input

I am trying to create a function that takes in an input $\mu$ and place that input into the replace rule for a numerical integration, as seen in the code below: ...
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1answer
83 views

Lévy C curve fractal from a substitution systems in NKS book p.190?

How can I make the geometrical transformation described in the page 190 in the New Kind of Science book by Stephen Wolfram to produce the fractal pattern? https://www.wolframscience.com/nks/p190--...
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1answer
51 views

Substitution of expressions in a symbolic expression

I define tables of symbolic variables in the following form (for convenience) ...
3
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2answers
58 views

Renaming expressions dynamically in Mathematica

I am trying to write a statement that will create a new positionVector as I parse through a matrix. What I am trying to accomplish would look something like this, For[i = 1, i <= vectorlength, i++ ...
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4answers
491 views

Replace sum x+y+z in expressions like 2x+3y+z

Related threads replacing-a-sum-of-expressions and Replace a sum of squared variables by a new squared variable Given the identity $x+y+z=p$ I'd like to simplify the generic expression $$kx+ly+mz$$ ...
3
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2answers
91 views

Creating an Array with Subscripts and Superscripts

I would like to figure out how to construct an array using subscripts and superscripts based on the following info: ...
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0answers
36 views

Are not rules applied in succession?

I am trying this: ...
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4answers
61 views

Only Reals Rules

I have a huge array of rules with many variables, such as ...
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1answer
41 views

commutator between tensor products

I am interested in some quantum mechanical calculations in Mathematica. I am working with a tensor product of Hilbert spaces $\mathcal H = \mathcal H_1\otimes \mathcal H_2$. I would like to implement ...
3
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1answer
122 views

Replace in Mathematica [closed]

I have: $$X=Z+22*Y$$ $$Y=P$$ Edited: Is there a way to replace $Y$ in the first expression using Mathematica? I tried Replace and it's not giving the desired result. Can I replace both Z and Y at the ...
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3answers
73 views

My rule does not do anything (understandably)

I want a rule that would transform, for example, And[i,F[j,k],l,G[m,F[j,k],n],p] into And[i,F[j,k],l,G[m,T,n],p], where ...
7
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1answer
197 views

How to replace only the isolated variable x

I want to replace the variable x in the result, not x in unrelated x[i]. ...
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1answer
29 views

Why does DifferenceRoot evaluate only in this table?

I would like to use a complicated function containing DifferenceRoot as a replacement rule, but somehow it evaluates only in ...
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0answers
55 views

How to plot a function using a table particular values

I would like to plot the following function in terms of kR, but using specific different values, I think the best easy way is using a Table. This is a common useful problem to explore numerical the ...
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1answer
52 views

Using MapThread and ReplaceAll together

I am trying to carry out some operations on the elements of dataset2, which is an 11 x 14 x 6 dimensional array: I have a function, ...
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3answers
87 views

Pattern matching involving a sum of wildcards

I am trying to implement the following substitution to an expression in Mathematica: ti den[a-ti] -> -1 + a den[a-ti] where ...
3
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1answer
49 views

Replace Condition in Replacement Rules

In finding an answer to my other question, I'm finding myself needing to manipulate the conditions imposed on replacement rules, but this is proving to be a little difficult. In particular, how ...
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1answer
43 views
1
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1answer
56 views

ReplaceAll with a list of parameters [closed]

Trying to ReplaceAll with a list of parameters, but I can't see how to do it properly: ...
2
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1answer
48 views

How to protect the expansion of exponent while applyting rules

I am trying to separate/split an expression (consisting of polynomials) to a list. However I want to keep the exponents intact. Here is an example: ...
3
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1answer
213 views

Mathematica can't replace integer multiple of 2 in power

I have some terms contain ww=a+a^2+a^6+a^-4 where (a^2)^p_. -> -dx[p] Exp[-x[p]] x^2 but Mathematica only replace power 2 ...
7
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3answers
334 views

Applying a function to every item in a column of a matrix

A problem that arises more often than I care for is that I want to modify specific elements nested lists. Examples may be wanting to add 1 to the second value, get ...
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1answer
52 views

Why does Replace `/.` not get evaluated in this formula?

Learning the wolfram Language, in section 32 "The Wolfram Language" // Characters[#]& /. Alternatives @@Characters["aeiou"] -> Nothing ...
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0answers
49 views

Simplification and patterns

I have a very simple simplification to make, where I need to do a replacement but the pattern matching seems slightly awkward. I would like to simplify: ...
5
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3answers
146 views

Conditional replacement element-wise

I have a $4\times 4$ matrix (symbolic). It has a variable, say jj, which should be $1$ for diagonal and $0$ for non-diagonal entries. I need to write a replacement ...
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0answers
48 views

ReplaceAll with named pattern [closed]

If k is unassigned, this yields {a, b, c}: ...
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0answers
22 views

Difference in pattern matching between Cases and ReplaceAll

I don't understand why there is a difference in the pattern matching between x a /. coef_*x^pow_. :> {pow, coef} and ...
2
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1answer
58 views

How to get the result in terms of a previously defined expression?

Say I have a vector X[n_] := Table[Subscript[x, i], {i, 1, n}] and a matrix of connections: ...
6
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1answer
119 views

How can I get the progressive application of list of rules?

I have a very long list of rules, and using this list of rules I want to see how some elements evolve as I successively apply the next rules on the previous rule. Here is the simpler version of my ...
4
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1answer
97 views

Turn definitions into rules

I know that this seems to be unnecessary, but here I have a bunch of assignments, like around 50, and I want to create rules for all these to have the freedom to apply these rules only on certain ...
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2answers
83 views

How to solve for y for a set of implicit (in x and y) linear equations for use in Plot?

From a matrix m={{1, 1}, {-1, 1}}, a vector b={1, 2}, and a list of variables vars={x,y} we ...
0
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1answer
28 views

Is there a better syntax to obtain the derivative of a function as a function/operator? (e.g. for simple plotting of derivtives of functions, etc.)

When trying to plot a derivative of a function, (I take Sin as a simple example), the naive approach ...
3
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1answer
84 views

Replace multiple variables using a list?

I want to calculate sum of derivatives of expression F = Exp[(x*z - 1) f*b + (x - 1) (1 - f) b] from n-th to (n-k)-th, say k=4. The dummy way which works is: ...
1
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1answer
49 views

Write function in terms of a combined variable [closed]

I am working with recursive convolutions of complex functions (fourier transforms), so, I calculate convolution integrals of functions of the form $$g(iy) = \int_{-\infty}^\infty f(ix)f(i(y-x))dx, \ \ ...
5
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2answers
137 views

How do I replace specific sequences of a sublist without changing the level of the list?

Suppose I have a list of multiple sublists: testlist={{1,1,1,0,0,0,1,1,1,0,1,1},{1,0,0,1,1,1,1,0,1,1,1,0}} I want to replace given sequences without creating new ...
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0answers
66 views

How can I shuffle the indices of certain variables?

I am recursively defining rational expressions in two sets of variables $x_i$ and $y_i$. Specifically, for $m<n$, I am interested in replacing all degree-$m$ monomials of the following form: $$\...
1
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1answer
24 views

Error: Root::npoly: not a polynomial in #1 [closed]

I have a $45\times 45$ matrix $H$ and its elements depend on $Ca$. I want to find its eigenvalues (which will also depend on $Ca$). I do this using: ...
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2answers
44 views

How to define a series of substituting rules?

suppose I have a long list of many variables: alist = { u, v, w, ... }. At some point, I have another combination of variables depending on { u, v, w, etc.},e.g., alpha = 2 * u + v beta = v + w^2. And ...
7
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4answers
205 views

How to use each replacement only once in a list of replacements

I have a list of replacements and some list they are acting on. However, some RHS of the replacements rules are identical (the LHS is not). I want to use those rules one after another (perhaps cycling ...
1
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2answers
42 views

How to match a formula in different level

Solve[4 n^4 + 4 n + 3 == 0] The result has many $$ \sqrt[3]{\frac{1}{2} \left(1+i \sqrt{3}\right)} $$ so I want to replace them with a letter, for example , ...
1
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2answers
50 views

Swap two numbers - but only in a particular context

I have a list of terms such as {2*s[1,2]^2, 3*s[3,5]^4, ...} and I would like to have a replacement that swaps $2 \leftrightarrow 4, 3 \leftrightarrow 1$, but only ...

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