# Tagged Questions

Questions about Mathematica's rule-based replacement functionality, including functions such as Rule (->), Replace, ReplaceAll (/.) and ReplaceRepeated (//.).

50 views

### Misunderstanding of Replace code

I am looking for the right way to replace $\delta \, \, \text{by} \, \, 0.05 \, \, \, \beta \, \, \, \text{by} \, \, \, 1.77 \, \, \, \text{and} \, \, \, n \, \, \, \text{by} \, \, \, 12$ in this ...
117 views

### Apply tranformation to particular list elements

I have a list with elements {a -> -1, b -> -2, c -> -3} If I now wanted to apply a tranformation to b and ...
69 views

### Is the replacement operator associative?

In mathematics, a given operation $\circ$ is said to be associative if there is equality $$(f\circ g)\circ h=f\circ(g\circ h)$$ for any $f$, $g$ and $h$. Intuitively, this means ...
444 views

### Random character change in a random place

I would like to ask for help in a Random Replace of character. For example: ORANGE and change 1 character randomly (random place and random character from ORANGE) in it into any character of ORANGE, ...
60 views

### Replacing elements in a list if contains X (string)

I want to replace T1 with T2 if the list contains X (It's a string with something more) or else return unevaluated. Input:...
43 views

### How to replace a hole mathematical expression? [closed]

I have the following function: Input: f=-a n^2/v^2 +v/n I want to Replace v/n by v_new ...
139 views

### Getting mathematica to factor out constants and apply euler's identity to a table

I'm doing some quantum mechanics homework that I'm going to eventually generalize to higher spin states, so the solutions are going to need to be decently independent of the dimensions of the table ...
168 views

### A replacement question

I have: {{θ -> 0}, {θ -> (2 π)/ 3}, {θ -> π}, {θ -> (4 π)/3}} I would like to create a list of points $(\cos\theta,\sin\theta)$ using each of the ...
66 views

### Type error before replacement rule is applied

When I type a <> "0" /. {a -> "1"} I get the error ...
142 views

### Replacement rule not having desired effect

So I have this replacement rule that tends to work in most cases, except occasionally in cases like this: ...
202 views

### Timing problem with ReplaceRepeated

I have the following data: ...
85 views

### On an existing notebook, how to transform all “double brackets” into “DoubleBracket”

Sometimes, having all double brackets [[...]] transformed into \\[LeftDoubleBracket] ... \\[RightDoubleBracket] can really ...
60 views

187 views

### Remove leading and trailing zeros from a list

This functions and gives the desired result: {1, 0, 2, 0, 0} /. {x___, 0 ...} :> {x} {1, 0, 2} But with leading zeros it doesn't: ...
47 views

### Collect fails to collect all powers of my variable [closed]

I am fairly new to mathematica and have not used it to really code anything at all, but just used it as an kind of advanced calculator. My issue is the following: I need to extract the power of a ...
94 views

### How could I perform this replacement?

I essentially have something of the form pm[1, 2] pm[3, 4] pm[5, 6] c[{1, 2, 5, 6}, "+"] c[{3, 4}, "-"] I want to add next to each pm a corresponding plus or ...
171 views

### Find the explicit solution of the integral

I want to calculate the integral: assuming that we are familiar with the relation: The answer should be: The code that I've used is the following: ...
211 views

### Converting set of characters into numbers using list of replacement rules

I am trying to convert a text, as an example "aaaa" into a set of numbers as defined in a list of replacement rules, for example letterstonum . letterstonum takes in letters a to z and returns the ...
59 views

### How can I perform this replacement? [closed]

I want to take an expression of the form p[1,2]p[3,4] and have an output of something like {{1,2},{3,4}} If I do the ...
110 views

### How can I force mathematica to calculate the integral and print the parametric result?

I have the following code: ...
53 views

### How to do this replacement without a for loop?

I'm new to Mathematica and I'm trying to get past my desire to use For loops for everything; can somebody tell me a simple way to make this replacement? I want my input to be ...
108 views

### MapAt with Replace(All) causing kernel crash

Bug introduced in 10.1 and fixed in 10.2 I wanted to roll a function that works like /. but only acts on the very first match it encounters. ...
86 views

### How to transform abstract finite group to permutation group?

It seems that Mathematica only has group functionality for permutation groups? Then there is a step to transform the abstract finite one to a permutation one. As an example, consider the following ...
213 views

### How to make a ReplaceAll Rule for adjacent items in a list?

I would like to make only one pass of a list of 2D items and replace adjacent items that have matching $x$ or $y$ coordinates with a series of linearly interpolated points between the two points. My ...
181 views

### How to change symbols in differential equation with a single rule?

Problem Suppose I have a differential equation such as $\qquad f'(x)+f(x)=0$ and I want to change it into $\qquad y'+y=0$ My Method Using rule = f[x] -> y,...
185 views

### How to replace an element in a list with an element in another list with matching indices

I have a list like this l = {1 + 2*s, 2 + 3*s, 4 + 1*s}, and I have calculated s = {1, 2, 3}. I need to replace ...
95 views

### How avoid error message with Range?

Evaluating Range[1, n] /. n -> 3 produces an error message ...
186 views

### Approximate UnitStep for use in Enterprise CDF

The following Manipulate code displays the VectorPlot for all functions. (This code is a subset of a more extensive notebook which is based on the structure you see below. Consequently, I need to ...
236 views

### Duplicate Mathematica functionality in Mathematica clone or lisp [closed]

What is the easiest way to accomplish the following in a Mathematica clone or in any version of Lisp? Also it doesn't appear in any lisps have a similar replace function. ...
33 views

### Substitute ratios

Suppose that I have the expression (x+y+z)/y. I want to substitute the rules Phix -> x/y, Phiz ->z/y. Is there a way to ...
322 views

### Pattern does not match with Orderless head

Why does the following pattern matching not succeed? ...
92 views

### Optimization of recursive functions by using the //. operator [duplicate]

In some cases, recursion in Mathematica (without storing values) is not very efficient. For example, the recursive implementation of Fibonacci numbers (version which doesn't store the values) : <...
73 views

### Changing notations for probability moments with subscripts

Suppose I have have two kinds of variables $X_{\alpha_j}, X_{\beta_k}$ in the form of Subscript[x,Subscript[α,j]] and ...
90 views

### Overriding the behavior of Dot

I would like to override the behavior of Dot, so that Dot[u,v] will return a scalar instead of a 1x1 matrix in the case that the ...
163 views

### Using NDSolve initial conditions as parameters for a function and then a replacement rule

I am trying to make a function based on two initial conditions of a set of differential equations: ...
73 views

### Replace symbol with numerical value

How do I get the same result, i.e., how can I get Mathematica to replace a with 1? ...
102 views

### How to assert that a list of variables is real in a nice and clean way

You can use the function Element to say e.g. $x,y,z\in\mathbb{R}$ via Element[x | y | z, Reals]. Now if I have a list of ...
54 views

### Replace function with multiple functions while respecting the inputs

I want to replace a function with either one or two functions and also combine their arguments. Say I have an original expression expr = u[i + 1] r[i] r[i-1] ...
63 views

### Why is the evaluation of f different using rules and using arguments to it as a function? [closed]

I will provide all the code I used at the end of the question. I was trying to evaluate a function f with the following signature (which I'll give the details at ...
196 views

### How does one unpack the contents of a list while using rules to substitute values for each variable?

My intention is having a large collection of variables (symbols to be more specific) in a list and substituting all the variables at once with a value using rule instead of going through each one, one ...
I have a matrix element $k_x$ and I want to substitute it as $-i\kappa$, I tried ...