# Tagged Questions

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

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### Converting an expression to modular arithmetic automatically

I have the expression $\frac{1}{15} \left(-(-1)^n-5\times 2^{n+2}+3\times 2^{2 n+1}+15\right)$ which I want to calculate mod m for a very large n. My current method is to ask for this exression in ...
709 views

### Truncate High order terms

Suppose I want to compute this : Series[Sin[1/f], {f, Infinity, 10}] but finally I prefer Sin[1/f] up to the fourth order in <...
88 views

### MapIndexed stops at levelspec 1 if only the index is passed?

If the function passed to MapIndexed references the first (or data) argument, the following performs as expected: ...
218 views

### Expand expression into quotient of negative power series

I have a function T(z) and want to expand it to the following form: At the end I want to have a list of equations, which can calculate a0, a1, a2, b0, b1 and b2 with different values of h1, h2, ...
545 views

### Conjugating symbolic expression

I am trying to conjugate a symbolic expression, and I have explicitly stated the real terms. However, I simply can't get it to work: ...
54 views

### expression contained across multiple cells

Is it possible to span one expression across multiple cells? E.g. long if statement or function evaluation. I looked in documentation and searched forum/google and could not find.
295 views

### Replace every Minus to Plus in Expression

Thought this is a rather simple thing, but I was not able to find a solution: I have a polynomial expression like: expr1=a^2-b+c*d expr2=a-b expr3=-a+b-c and ...
105 views

### Decompose Expression into Segments

Say I have an expression test = 3 x1^2 - 2 x3^-3 and I would like to decompose the expression into {3 x1^2, -(2/x3^3)}, I can do ...
90 views

### Working with functions

I am required to write a function that takes a function as a parameter. ...
726 views

### List manipulation to build a functional expression

Since Mathematica deals with Head[a, b] as an expression in this way The first Part of Head[a, b] is ...
164 views

### Patterns of function-arguments in expressions

I want a function that compares an expression with a specific pattern. The expression has always the following form: ...
143 views

### Selecting expressions from a sequence that are not subexpressions of earlier elements

I have a While loop that generates and prints an expression on each iteration (there can be thousands of iterations). UPDATE: Some expressions are generated in ...
240 views

### Extracting function calls from an expression

I have an expression like this: expr = F[0, 1] + 2 F[0, 0] - 17*F[2, 0] and I want to transform it to a list consisting of all function calls with its arguments: ...
129 views

### Merging two held expressions into a held compound expression

Consider e1 = Hold[a = x + x; b = y + y + y]; e2 = Hold[c = a + a + b + b + b; c^2]; How can I obtain the following? ...
85 views

### How to combine DifferenceRoot objects for odd and even-indexed terms

I'm trying to analyze a certain infinite sequence $S$, indexed by positive integers starting from $1$. It can be split into two subsequences: $S^{odd}$ by removing all even-indexed elements and ...
189 views

### Partial result of aborted evaluation of FullSimplify

When FullSimplify invoked on a large expression, it can run for hours. If I do not have time to wait, and abort the evaluation, I get no result, although, ...
110 views

### Why is ^^ff not the same as ^^ToExpression[“ff”]?

I want to convert a hexadecimal string to a decimal (base 10) number: 16^^ff 16^^ToExpression["ff"] The 1st line returns the correct answer of 255, while the 2nd ...
255 views

### Set gives an unexpected error message (Set::partw)

Here is a minimal example: s = 1 /(a + b[3]) + 1 /(2 a + b[3]); s[[1]] = Sum[s[[1]] /. b[3] -> k, {k, 3}] s[[4]] s[[4]] = Sum[s[[4]] /. b[3] -> k, {k, 3}] ...
112 views

### How to convert the expression '{a->a0, b->b0}' to the expression 'a=a0; b=b0'? [duplicate]

How to convert the expression '{a->a0, b->b0}' to the expression 'a=a0; b=b0'? I think this is a common question and do not know if someone has asked it before. Any help or suggestion will be ...
2k views

### How to extract expression from ConditionalExpression

p1 := y /. {First[Solve[x^2 + y^2 + x == 1, y, Reals]]} ...
222 views

### How to collect expressions from cells created by Print?

I have a notebook where evaluation of a certain cell produced hundreds of adjacent output cells using Print. I need to create a list containing all expressions from ...
100 views

### check if the expression is a equation

I need to check if the expression is a correct equation with only 1 variable x and without functions, that are not build into Mathematica. For example Sin[x]==0 ...
79 views

### How to bail out from a non-applicable transformation function?

I provide a custom function in TransformationFunctions options of FullSimplify that can do a transformation only for some values ...
463 views

### Replace doesn't replace the denominator [duplicate]

I have the following expression in Mathematica -((E^(2 - 2 Sqrt[(x[1] - x[2])^2]) (x[1] - x[2]))/Sqrt[(x[1] - x[2])^2]) I want to replace anything of the ...
680 views

### How to extract a possible closed form from WolframAlpha[] output

To find a possible closed form of a number, I can use the function WolframAlpha["6.38905609893065", IncludePods -> "PossibleClosedForm"] It returns a result ...
111 views

### Operations on expressions within Hold [duplicate]

I want to convert {Hold[1 + 2], Hold[3 + 4], Hold[5*6]} into Hold[{1 + 2, 3 + 4, 5*6}]. I have tried ...
44 views

### Matching Root[…] objects with patterns, unexpected hidden argument

I needed to write patterns that could distinguish between arbitrary-function and polynomial forms of Root objects, for example, ...
62 views

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### Why is ToRadicals[] not able to handle all cases? Is there a workaround?

The documentation for the function ToRadicals says: â™¦ There are some cases in which expressions involving radicals can in principle be given, but ...
715 views

### How to automatically get rid of trig functions in an expression?

I have a large expression containing many terms like this: Sin[1/2 ArcTan[(2 Log[5])/(Log[5]^2 - 2)]] where a trig function is invoked on a rational multiple ...
117 views

### Need a generalization of RootApproximant to recognize linear combinations over algebraic numbers

RootApproximant does a very good job when I need to recognize an algebraic number and when enough of its digits are known (or even when an unlimited number of ...
308 views

### How to reduce the number of operations needed to evaluate an expression? [duplicate]

For some numerical calculations in C++ I have, for example, this complicated expression to evaluate. Given as Mathematica input, in its original form it is ...
37 views

### Detecting a more general pattern [duplicate]

I need a function that, given 2 patterns, determines if the first pattern is more general than the second (i.e. that any expression successfully matched by the second, will be successfully matched by ...
181 views

### A question about derivatives (cubics)

Given an equation: f(z) = a (x + I y)^3 + b (x + I y)^2 + c (x + i y) + d Which can be re-written as: ...
343 views

### Getting a usable expression tree

I need to get the expression tree for some expression. expr //TreeForm The above grabs the expression tree but it isn't in some sort of usable format. Just an ...
229 views

### Passing list of options to Plot

I'm looking for a way to create a variable that I can use to hold all of the graphics directives for, say, a plot command. For example, I have 8 plots with variations on the following: ...
183 views

### How to unthread?

For example {a + b} == {c + d} // Thread (*{a + b == c + d}*) how to get {a + b} == {c + d} from ...
143 views

### What are the scoping rules for function parameters shadowing System symbols?

Here are some very contrived code snippets, highly unlikely to appear in real code, but still I am curious why they behave like this: ...
156 views

### Assigning Sequence to Part of a SparseArray (bug?)

Part â–ª You can make an assignment like t[[spec]]=value to modify any part or sequence of parts in an expression. â–ª If <...
88 views

### Why is NHoldFirst not propagated to symbolic derivatives?

I encountered a nasty problem that N cannot evaluate expressions containing a symbolic Derivative of a multi-parameter function ...
274 views

### What are the default TransformationFunctions used in Simplify and FullSimplify?

If I do Simplify[(c^3 - s^3)^2 - (s^3 + c^3)^2, TransformationFunctions -> Automatic] (i.e. a verbose version of default behaviour), what transformation ...
1k views

### How to import a Microsoft Word document into Mathematica?

I have a Microsoft Word document in DOCX format. I need to import it into Mathematica as a String preserving all formatting (font, size, bold/italic style, colors, ...
381 views

### How to convert an image to a compressed string representation equivalent to one copied to clipboard by CopyToClipboard[image]`?

In my recent question I asked How to embed an image into a string? The suggested solution was ...
386 views

### How to decompose a complex expression containing repeated subexpressions? [duplicate]

Suppose I have an expression like ...
1k views

### How can I get Mathematica to write Log instead of ArcTan?

ArcTan really bothers me, so is there a way to make Mathematica write Logarithm instead of ...
332 views

### Symbolic manipulation of functional form

I have a functional polynomial expression of the form: ...
640 views

### Comparing Mathematica expressions like diff

I am looking for a way to compare (or "diff") two Mathematica expressions, similarly to how to diff utility can compare two text files and report the differences. Has anyone already written such a ...
191 views

### Examine function parameters programmatically

I write a lot of scripts in Mathematica and I'd like to eliminate the boilerplate that parses command-line arguments and assigns them to variables of the correct type before doing the real work. I was ...
I have a symbolic matrix $$m = \begin{pmatrix}A1 & B1 & C1\\A2 & B2 & C2 \\ A3 & B3 & C3\end{pmatrix}$$ and I believe that Det[m] is ...