Questions tagged [expression-manipulation]
How to manipulate expressions structurally, not necessarily complying with the rules of algebra.
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Save expression for future use [closed]
I have an expression given by a summation, which takes a few hours to compile and which gives me over a million terms.
How can i save up this expression to use him another day, wihtout doing the sum ...
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Pattern not matching BoundaryMeshRegion
Mathematica 13.1 on Windows 10.
Can someone explain why the following does not match:
MatchQ[BoundaryMeshRegion[Cube[]], BoundaryMeshRegion[__]]
(* False *)
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How to attach Upvalues to CompoundExpression?
I'm trying to make something like this work:
Evaluating
someData // Query[whatever...] /* summarizeInPrettyWay /* promptToRemoveCompoundExpression ;
should produce
...
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How to remove branches in Piecewise with measure 0
I am doing Convolve over UnitTriangle in 2 dimensions and the resulting piecewise function has conditions with measure zero (...
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Extracting elements from a List in a specific way
I have a set of polynomial expressions in multiple variables:
...
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Find the smallest subexpression containing all subexpressions matching a given pattern
I need to write a function that, given an expression like
1/x + 1/(Abs[x] + 1/(1 + Abs[y - Abs[x]]))
finds all its subexpressions matching a certain pattern (say, <...
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Given the expression of `x`, how can I eliminate the terms that tend to zero as `x` goes to infinity but keep those which are non-zero or infinite?
Suppose I have an expression of x. Now I want to somehow evaluate its "limit" at x->Infinity, but in such a way ...
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Back-substitution
Suppose that we have an expression (expr in the code below) and replace a long term with a new parameter (K).
For a simple example;
...
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Replace subexpression with variable in result from Laplace transform
I'd like to clean up the result I obtained from an inverse Laplace transform:
First of all, I'd like to replace the square root expressions in the hyperbolic function arguments (part encircled in ...
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A complicated derivative problem
I have some equation，like this
$$
\begin{aligned}
&\hat{t}_{g o}=\frac{R}{V_{m}}\left(1+\frac{(n+2) \sigma^{2}+(n+1)^{2}(n+2) \sigma_{f}^{2}}{2(2 n+3)(2 n+5)}-\frac{(n+1) \sigma \sigma_{f}}{2(2 n+...
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CellObject[Number] to its content
As in the following sreenshots, roughly speaking, Out[43] is CellObject[97601].
I want to set ...
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TreePosition with multiple (not just node data) conditions
Given a Tree object, TreePosition takes patterns only on the "data" of the node plus a level spec.
...
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Symbolic PDE manipulation
I'd like to transform a PDE in a way such that I can express a temporal derivative as a spatial derivative using some known relation.
Very simple example:
...
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Confusing abnormalities observed when counting a specific operator in an expression [duplicate]
Recently I have met with some confusing abnormalities when trying to determine if there is a specific operator (usually Plus[] ) in an expression by programming. ...
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Extracting the constant term
Finite difference problem
There are a large number of variables, interacting at most five at a time. A sample term is:
How to extract the constant term?
In this example, the constant term is -1/4.
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Factorize expression by specific term [closed]
I am new to Mathematica but I would like to know how to force Mathematica to factorize an expression by a specific term.
Exemple, imagine I have a term like this:
And I have an expression like this:
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Can one collect with respect to two groups of variables?
Here is a toy example of what I want: given
...
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How to extract logarithmic terms in an expression?
I have some expressions of the type
$f(x) \,+\, g(x) \,\log(x) \,+\, h(x) \,\log(1-x^2)$
where $f$, $g$, and $h$ can be any rational functions of $x$. I am trying to use Mathematica to extract each ...
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Why does my list of positions contain a leading and following element not in the original list?
I have a list which contains non-integers (three in this case) each of which I need to replace with a different Random Variate.
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Get rid of some solutions proposed by Reduce/Solve
I would like to take the result of a Reduce function call and eliminate any solutions that depend on the value of a particular variable (call it $y$). For instance, I am trying to get the parameters ...
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How do I extract the component from an expression
I'm embarrassed that I don't even know the language for what I'm asking. The result of an operation I'm performing is:
$$expression=-dt^2 \left(c + a t\right)^2$$
$dt$ is basically an infinitesimal in ...
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Speclevel in Reverse
I have an expression involving several dot products, I give a simplified example:
expr={A.B,C.D}
I want to reverse all dot products, and try
...
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Separating terms in an expression with many variables by their "nature"
I have an expression like this:
$f=t_1(\sin(\alpha),\cos(\beta),\cos(\gamma)^2) \cdot r_1(x,y,z)+t_n(\sin(\alpha),\cos(\beta),\cos(\gamma)^2) \cdot r_n(x,y,z)$
Where $t_i$ and $r_i$ - functions of ...
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Can Mathematica simplify expressions with prescribed relations?
I have a linear map $T$ on a vector space which satisfies $T^4 = 1$ and want to simplify expressions of the form:
$$[X,TY] + [Y,TX] + [Y,T[TX,TY]] + [X,T[TX,TY]],$$
where $[\cdot, \cdot]$ denotes the ...
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How to use RightComposition efficiently in the context of one-liners?
I find myself recently writting, more often than not, code that makes heavy use of RightComposition eg.
expr//f/*g/*h
It is relatively straightforward to first ...
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How to convert Graph atomic object back into unevaluated expression? [duplicate]
For the purposes of further development of my shortInputForm function, I wish to convert Atomic objects such as Graph into non-...
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Extract first term of each element in a list
Suppose I have a list of the form
list={a+b,c+d,Xi+Psi*Zeta,0}
How can I make a list of only the first term of each element in that list? In this case the list ...
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How to convert this Mathematica expression to another, as described here?
I am working on a function of which the core will consist of something like:
...
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Get depth of vertices in TreeGraph
I want to get the depth of each vertex in a TreeGraph, g. I might convert g into an ...
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Encode expression into a list
I have an expression of the form:
$$c {\partial^{k+l} \Phi(\theta,\phi,n) \over \partial \theta^k \partial \phi^l}$$
$n,k,l$ are (positive) integers. $c$ is some constant. It is also possible that $c$ ...
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Converting an indefinite integral to definite integral
For example, I have the following integral expression:
g[x, y] = Integrate[f[x, y],x]
How can I modify the above expression to achieve the following definite ...
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Factoring an arbitrary power from the rest of the expression in an exponential expression
I have the following expression:
Exp[r*t*x + e*r*y + t*x*r^2 + y^2*e*Sqrt[r]]
I want to choose some arbitrary terms in the power and for example write the ...
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Simplifying multiplies of sums into a single double sum
I have the following expression:
Sum[x^n, {n, 1, Infinity}]*Sum[Log[m, x], {m, 2, Infinity}]
How can I Force Mathematica to write this expression in the following ...
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Transforming one exponential expression to multiplication of exponential expressions [duplicate]
I have the following expression:
Exp[a * x + b * y + c * z]
I want to write this expression as:
...
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How to express Bessel Functions in terms of Hankel Functions
I have the following expression
BesselJ[\[ImaginaryI]*m, k*r]
FunctionExpand knows how to transform from ...
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How can I extract a list of terms with functions in terms of a specific variable
I have an expression in the following form:
a f[x] + b Exp[g[x, y]] + r[z] f[y] + f[y] Sin[h[x, y, z]^2] + r[z] Log[t[z, y]]
I want to extract an expression ...
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Same displayed expressions produce different outputs
I know EngineeringForm is a wrapper which prevents evaluation of content, but pasting chunks of other cells with an EngineeringForm number, got these two simple expressions w/ the same input ...
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How to make a function in terms of constants to inherit the attribute of being constant
I have defined two variables a and b:
SetAttributes[a, Constant];
SetAtributes[b, Constant];
I have defined a function c as ...
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Extracting expressions from LHS of an assignment
I need to list all variables in a notebook containing several Set assignments, lhs=rhs, and equations, ...
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Equality of expressions with different variable names
I have some multivariate systems of expressions that I want to check for equality up to allowing relabelling of the variables. For example the two expressions below would be the same:
...
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How to locate a value from a list
I made a list with two values in each cell.
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Denoting the whole in Position/Extract/ReplacePart
Position returns lists of numbers consumed by Extract, ReplacePart and others as "...
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Coefficient works on $\pi$, $x$ and $x^2$, but not on $\pi ^2$
Consider
(\[Pi] + 2 \[Pi]^2 + 3 x + 4 x^2)
Executing
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Manipulation of expression
Let
ss2 = (γ + ν)/β;
is2 = ((γ + ν)/β) (β/((γ + ν)) - 1);
I wish to do the following computation but want to keep the output in terms of ss2 and is2:
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