# Questions tagged [expression-manipulation]

How to manipulate expressions structurally, not necessarily complying with the rules of algebra.

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110 views

### Conflict with hidden names

The following code hangs Mathematica 12.0.0: ...
93 views

### Strange behavior of Apart

Here is a piece of sad comedy based on some Apart behavior. Is there a way to make Apart do the expected step? Consider a very ...
67 views

### Is there a good reason why Slot[] is not an atomic expression?

Here's a good reason why I think it should be, Map[ If[AtomQ@#, #->"is an atom", #->"not an atom"]& , {"hello",Range@3, # &} , {-1} ] ...
128 views

### How to replace $x$ and $x^2$ with different value?

I have an expression now expr = x + x^2 what I want to do is to replace $x$ with $k\times p$ , and $x^2$ with $[k\times p + k\times(k - 1)\times p^2]$. The ...
40 views

### Narrowing the range of an interpolating function while keeping integral the same?

Consider an interpolating function derived from some data, e.g. ...
39 views

### Expandable summary view for a large expression

I need a convenient interface to interactively explore very large expressions. I am aware of Short and Shallow, and appreciate ...
16 views

### Expressing Numbers with Rational Denominators (Surd Form) [duplicate]

Is there a command which expresses given real numbers in surd form (when possible)? That is, a form where any rooted terms are placed in the numerator, and the denominator is rational. Here are some ...
36 views

### Replace sub-expressions matching a pattern unless located under specific heads

Suppose I have some rule, e.g. Re[x_] :> (x + Conjugate[x])/2. I want to apply it to all matching sub-expressions in some expression, excluding any sub-...
35 views

### How the terms are arranged in CoefficientList command?

I have an expression containing various orders (powers) of F[r]. Using CoefficientList, the output is a blue box which is ...
71 views

### Exclude the terms from determinant

i have a long determinant expression such as delta=8+2a+3b+4c+50a^2+2a^3+70b^2+80a*b+20(a^2)b+5(e^x)+a*b(e^x)+....+3e^(-x)+.. I want to exclude the expression ...
30 views

### Wrong derivative for a function that I try to define without explicitly giving number of variables

What I actually want is to define functions depending on the number of variables which will be specified during some computation. My (probably wrong) attempt is ...
263 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 ...
110 views

### Group symbols by a given partition of the occuring symbols

I have following expression $$-3 b_{\sigma _d}-3 b_{\sigma _v}-b-b_2+2 j-2 j_2-2 j_3+2 j_6+12$$ Mathematica input ...
50 views

### How to use replace for only one term in a long expression in Mathematica?

I am doing some Cauchy integration and in some intermediate steps I have something that looks like that: (..many_terms...+I*\epsilon(k1-p1))/k1 where ...
38 views

### Why does Refine not use transformation rules for a user-defined function?

I defined a transformation rule for a symbol L that takes a sequence of numbers ...
42 views

### Generating examples by applying conditions to symbolic expressions

For example, Given a list of symbolic expressions: ...
28 views

### Obtaining part of an expression from a position [duplicate]

I would like to recover a subexpression from its position in the expression. For instance: Position[{3, {3, 5, {6}}}, 6] returns the position of 6 in the ...
57 views

### How to show the sign of an algebraic expression?

I defined a long expression ...
541 views

### How can I obtain a complete list of the kinds of atomic expressions in the Wolfram Language using only the language itself?

I mean, Wolfram is a language--it's words are infinitely combinable. According to answers to my last question, the only way I can find out if an expression is atomic is actually use the expression. ...
67 views

### How can I ask the Wolfram Language to tell me if a hypothetical expression with a particular head would be atomic or not?

Integers in the Wolfram Language are atomic expressions, while uses of the Map function are not atomic. But if you didn't know this, how could you find out using only the Wolfram Language? The best I ...
101 views

### Why do atomic objects like 56 have a head if they're supposed to be, well, atomic?

This question follows from this one I made earlier. If you ask for FullForm you will get back 4, and that's fine. ...
35 views

### Selectively changing precision while leaving integers and rationals unchanged

I didn't find an answer to this question on the site, but as I was writing up my question, I figured out how to do it, so I thought I should post it and answer my own question so that others can ...
42 views

### Manipulation using Together[]

The use of Together either cancels the common factor from numerator and denominator or multiplies them with a common factor. In my code I do not want that ...
119 views

### How to import latex matrices into Mathematica?

I have a lot of $\LaTeX$ matrices, and I want to find their eigenvalues and eigenvectors. I tried to import them to Mathematica with: ...
31 views

### Expression manipulation with exponential

I have the following expression a + b + c + x + y + z + r*E^m + s/E^m + t*E^n + u/E^n I want to extract the coefficients of exponential terms as well as the ...
220 views

### Iterate over deepest values in a nested Association

Is it possible to iterate over the values of the deepest layer of keys in a nested association? For example: ...
89 views

### Need help in understanding what Extract does

Can anyone explain two examples from the Mathematica Documentation Center reference page on Extract? One is: ...
91 views

### Applying functions to leaves of nested list structure, when these leaves are more complex expression trees [duplicate]

Is there a way to apply a function h to the following nested list {{a, b}, {c, d}, {{d, e }, {f, g}}} where this should should become ...
47 views

### Dimensions of list used in test

I would like to reduce the number of brackets in a list for nested lists containing 1 sublist. For instance {{1,2,3}} should become ...
31 views

### Grouping expressions by associative equivalence for a single operation

I would like to group expressions under associative equivalence, but only for a specific operation used in the expression (not for other operations). Say we have two binary operations A and B ...
58 views

### How to decompose an expression into basic forms (e.g. a[] to Part[a, 1], a=1 to Set[a, 1], etc.)? [closed]

Is there something I can call in Mathematica to figure out the composition of a given expression? I want everything decomposed to the most basic f[a, b, c] format.....
55 views

### Groupings over non-atomic elements

I use groupings as below: Join[ Groupings[IntegerPartitions, {A -> {2, Orderless}, B -> {2, Orderless}}], {x}] Which generates: ...
27 views

### Groupings: orderless version?

Consider the following groupings code: Groupings[IntegerPartitions, {A -> 2, B -> 2}] This generates: ...
88 views

### How to simplify an expression by substitution?

Sometime Solve and DSolve give a finial form of the solution, which is fine in may applications. However, in some cases, one may ...
131 views

### Neat redistribution of association values

Given an original association: original = <| "a" -> {a1, a2}, "b" -> {b1, b2}, "c" -> {c1, c2} |> and a set of redistribution rules e.g. <...
126 views

### How to write down a product with omitted terms?

I have the following term which I would like to express correctly in Mathematica: $$\prod_{j=1,j\neq i}^m(\rho_i-\rho_j)$$ Can you please help?
63 views

### Collecting the derivatives of a sum

I have an expression where thereare many terms that involve the sum of the derivatives of two functions like $\qquad G^{(n)}[\lambda]+q^{(n,0)}[0,\lambda]$ I wanted to use ...
84 views

### Keeping specific terms in Mathematica output

Update: After solving an equation I came up with a complicated expression, is it possible to only keep some specific terms of an expression ? As an example, if the expression is: How can I keep only ...
44 views

### How do I force a fractional coefficient to exclude non-numeric symbols?

Short version of question: Suppose I have an expression: expression = a+3b; When I divide by 2, I get: expression/2 It is ...
459 views

### Custom atomic expressions - modern tutorial

Atomic but sophisticated expressions are all around for a long time: Graph SparseArray. More are coming witch each new release,...
70 views

### How do I extract the matrix from an density matrix equation?

I have a density matrix equation and I wish to put it in the form of a matrix. For example, if I have: $$\rho =Ax_{1}x_{1}+Bx_{1}x_{2}+Cx_{2}x_{1}+Dx_{2}x_{2}$$ Copy-and-paste version ...
52 views

88 views

### Get the intermediate steps of FullSimplify

I have this expression: Log[i] > (i Log[i])/n + Log[n - i] - (i Log[n - i])/n And I attempt to simplify it and get this: ...
57 views

### Require an expression to be formatted as an exponential expression

How can I require Mathematica to format an expression like Exp[x] x^s as Exp[x + s Log[x]]?
21 views

### How to separate nested subexpressions to list?

I have an expression like this: 3*Subscript[v, 0]^3*Subscript[v, 1]^8*Subscript[v, 2]^7*Subscript[v, 3]^2 I would like to extract the exponents and put them into ...
52 views

### How to solve a Poisson's differential equation with a boundary condition at infinity?

Context: This question is relevant to the physical problem of calculating potential for a set of p-n-p junctions. We have to solve a Poisson's differential equation for a p-n-p junction with ...