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Results tagged with symbols
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user 9362
Mathematica symbols are the ultimate atoms of symbolic data. Every symbol has a unique name, exists in a certain Mathematica context or namespace, and can have a variety of types of values and attributes.
8
votes
What are the requirements for a well behaved indexed variable? Subscript, ToExpression, Down...
Using DownValues enables you to format the display in the subscripted form without using Notation and Symbolize
(Format[#[n_]] := Subscript[#, n]) & /@ {x, σ, a};
kvar[k_] := Through[{x, σ, a}[k]]
…
- 163k
4
votes
Accepted
Separating variables in an expression
expr = x z Sin[x] Sin[y];
f = Variables[Level[#, {-1}]] &;
If the order is not important
Times @@@ GatherBy[List @@ expr, f]
(* {x Sin[x], z, Sin[y]} *)
If you want them ordered by variable
…
- 163k
4
votes
Can you use superscripts as variable and function names?
ClearAll["Global`*"]
Format indexed variables
(Format[#[n_]] := Superscript[#, Row[{"(", n, ")"}]]) & /@
{z, w, a, b};
The function definition is
z[1][x_, y_, z_] := x*y + z
With your specific a …
- 163k
4
votes
Accepted
How can i replace the symbols in a list?
Look at the FullForm of a Rule
a -> b // FullForm
(* Rule[a, b] *)
SeedRandom[1234];
b3 = Thread[{a, b, c, d, e} -> RandomInteger[100, 5]]
(* {a -> 8, b -> 72, c -> 44, d -> 38, e -> 22} *)
b3 /. …
- 163k
3
votes
Accepted
Replace symbols in output without evaluation
expandNCM[(h : NonCommutativeMultiply)[a___, b_Plus, c___]] :=
Distribute[h[a, b, c], Plus, h, Plus, ExpandNCM[h[##]] &]
expandNCM[(h : NonCommutativeMultiply)[a___, b_Times, c___]] :=
Most[b] Ex …
- 163k
3
votes
Free symbols in an expression
x = a + b;
y = Defer[x*x + g] + 6 x*c + Pi*d + Sin[a*E];
Variables@Level[y, {-1}]
(* {a, b, c, d, g} *)
Variables@Cases[y, _Symbol, -1]
(* {a, b, c, d, g} *)
EDIT:
y = Defer[x*x] + HoldFor …
- 163k
3
votes
Matrix of functions
Recommend that you consider using an indexed variable.
labels = {"A", "B", "C"};
If f[x, y] is distinct from f[y, x]
ClearAll[f]
Format[f[x_, y_]] := Subscript[f, ToString[x] <> ToString[y]]
(m …
- 163k
2
votes
A problem when solving an equation with symbolic variables
Clear["Global`*"]
sol[eq_] := Solve[Cases[eq1,
c_ *_Dot :> c, Infinity] == 0];
eq1 = (a[3] - a[4]) ψ . ξ + (a[1] + 2 a[2]) ψ . ϕ;
sol[eq1]
(* {{a[2] -> -(a[1]/2), a[4] -> a[3]}} *)
For the o …
- 163k
2
votes
Accepted
How to use the SymbolName of variables along with Map and pure function
Enter values as strings and convert to expressions.
EDIT: Added Opacity control
Manipulate[
A1 = {-1, 0, 1};
A2 = {Cos[α], Sin[2 α], -2};
With[
{polyw = PolyhedronData[poly, "Polyhedron"]},
G …
- 163k
2
votes
Accepted
Programmatically defining variables
Clear["Global`*"]
It is much easier to use an indexed variable and use Format to display the variable any way that you want.
For example, to display μ as a subscripted variable
Format[μ[n_]] := Subsc …
- 163k
2
votes
Difference between (Names of ) Symbols and Mathematical Objects
$Version
"13.2.0 for Mac OS X x86 (64-bit) (November 18, 2022)"
Clear["Global`*"]
Assigning a value to OverHat[x]
OverHat[x] = 3
(* 3 *)
OverHat[x]^2 + 3 OverHat[x] + 1
(* 19 *)
Clear the value …
- 163k
0
votes
Accepted
Testing Expression over region of values
Clear["Global`*"]
expr1 = ((1 - (a*x))^12)*((1 + (a/b))/((1 + (a*x/b))^2)) // Simplify;
Evaluating the integral
int = Assuming[0 < a <= 1 && 0 < b <= 1,
Integrate[expr1, {x, 0, 1}] // Simplify] …
- 163k
0
votes
Using the symbol of the system of equations
eqns = {x + y + z == 1, x - 2 y + 4 z == 2, x + y == 1};
Grid[{
{Style["{", 18*Length@eqns, Gray], First@eqns},
Sequence @@ ({SpanFromAbove, #} & /@ (Rest@eqns))},
Alignment -> {{Right, "=="}, …
- 163k