For questions about symbolic computation, as opposed to numerical computations.
4
votes
1answer
94 views
Identical code, different answers?
I'm having some trouble with identical code giving different answers. On a fresh kernel (MM 9.0.0.0, Windows 64-bit), running the same code, copy-paste, gives two different answers:
...
4
votes
1answer
255 views
How to symbolically differentiate an infinite series without evaluating the series itself
I'm dealing with finite sums of infinite series. Each of the infinite series possesses a different starting index, i.e. each of the series begins at n = 0, n = 1, or n = 2. As a result, it's important ...
4
votes
2answers
83 views
Problem with adding vector to symbolic function (for NDSolve)
I'm trying to set up a system of differential equations for passing to NDSolve. Note that my initial conditions are vector valued so Mathematica should know that ...
4
votes
1answer
158 views
Simplification of double symbolic sums containing a DiscreteDelta without explicit summation range
I am trying to get Mathematica to automatically do simplifications like the following:
$$\sum\limits_{q}^{q\in qV}\sum\limits_{q'}^{q'\in q'V}{f(q)g(q')\delta(q-q')}=\sum_{q}^{q\in qV}{f(q)g(q)}.$$
...
4
votes
0answers
72 views
Using Resolve and ForAll to prove takes a really long time
I've been trying to prove a lemma for my paper using Mathematica... basically that
$$\forall \{n, d_i, d_j\} \in \mathbb{Z},\ n \ge d_i > d_j \ge 2$$
it's true that
$$V[1, n, d_i-1, d_j-1] ...
3
votes
3answers
206 views
Efficient code for solve this equation
We have know $a*b*c=-1$, $\frac{a^2}{c}+\frac{b}{c^2}=1$, $a^2 b+a c^2+b^2 c=t$,
What's the value of $a^5 c+a b^5+b c^5$?
I tried
...
3
votes
1answer
148 views
What properties make this equation difficult to symbolically solve?
I tried to solve the following equation with Mathematica's solve:
Solve[K*(2*Tan[L/2*Sqrt[P/(EI)]]-L*Sqrt[P/(EI)])+4*P*Sqrt[P/(EI)] == 0, P]
It gave the ...
3
votes
1answer
145 views
Non-commutative algebra
I'm constantly dealing with non-commutative algebras. ** is inbuilt, non-commutative and associative. That's good :-) But it is not distributive. Rats.
...
3
votes
1answer
391 views
Definite and Indefinite integral give different results for piecewise function
I have the following function:
$$
f(q,y)=
\begin{cases}
\tfrac{11720+p}{37791360} & -11720<p<-7720 \\
0 & \text{True}
\end{cases}
$$
where $p = 443\ y-777600\ \sin^{-1}\left(\frac{q ...
3
votes
1answer
42 views
Non commutative multiply- expand expression
I began to use Mathematica a few days. My problem is: How to expand expression like $(a+b)*(a+b)$, where this multiplication is non commutative? Mathematica can do this?
3
votes
1answer
333 views
Symbolic integration in the complex plane
Context
While answering this question, I defined (symbolic and numerical) path integrations as follows
...
3
votes
1answer
106 views
Identifying `Indeterminate` elements [closed]
I want to identify if a variable, which is the result of a calculation, is Indeterminate. I was trying to do this using If[]. ...
3
votes
1answer
267 views
Computation of parametric integral
I am trying to compute the integral
Integrate[(g^(u^(g - 1)))/(1 + u^g), {u, 0, t}]
but as an answer I get my input expression. There must be something wrong ...
3
votes
1answer
168 views
n-fold symbolic integral in Mathematica
I am trying to compute symbolically a n-fold integral (n is a parameter of a function) over, say, the cube [0,a]^n. My code looks like this
...
2
votes
3answers
239 views
Symbolic derivative of $n$-term product
I want to determine the relationship that must exist between the $x_i$ and $y_i$ such that
$$
\frac{\partial}{\partial\theta} \prod_{i=1}^n \frac{f(x_i,\theta)}{f(y_i,\theta)} = 0,
$$
where
$$
...
2
votes
2answers
270 views
Superscript prime symbol
x\[Prime] looks like $x_'$, ugly right?
Is there a way to make a symbol with prime to look like $x'$?
That's what I'm trying right now:
...
2
votes
1answer
168 views
Identifying the sign of an expression in an interval
My expression is the following:
$$
\frac{(1-\alpha ) \alpha h^2 (h+2) \mu r}{(h+1) ((1-\alpha ) h+1) (\alpha h+1)}-\left(\frac{\alpha h \mu }{h+1}\right)^{\alpha } \left(\frac{(1-\alpha ) h \mu ...
2
votes
3answers
271 views
How to calculate partial derivative of an unknown function
How can I force Mathematica to calculate symbolically the partial derivative of a function u[x,y] with respect to a variable ...
2
votes
1answer
150 views
symbolic integration of a definite integral, how to speed up
I am wondering what are the general tips & hints for speeding up symbolic integration. As far as I understand, it solely depends on the form a function is represented before it is processed by ...
2
votes
1answer
155 views
Difference between Map[f[#] + g[#] &, {a, b, c}] and Map[f[x]+g[x]&, {a, b, c}]
Map[f[#] + g[#] &, {a, b, c}] vs Map[f[x]+g[x]&, {a, b, c}]
My question is: why is the output different?
...
2
votes
2answers
161 views
How to find solutions that yield of root of unity?
I have a polynomial with coefficients that are integer polynomials in another (complex) variable. For example:
1 + (1 - v^2) #1 + (-3 - v^2) #1^2 + #1^3 &
I ...
2
votes
1answer
122 views
Simplification of a symbolic manipulation involving functions of more than one variable
I am facing the following problem.
f[x_,y_] = a[x] u[y] + b[x] v[y]
Now I can ask Mathematica to calculate
...
2
votes
2answers
88 views
Mass Symbolic Manipulation with Subscripts? (from plaintext Input)
The simplest example of the change being sought is a greek letter, typed in as plaintext nu, and its may be replaced by the symbol, ν:
expr = 3nu*kx*ky+ ...
2
votes
1answer
96 views
Is it possible to create a compiled function with some symbolic arguments?
I am trying to create a compiled function that takes in several arguments. However, some of the arguments contain symbolic entries and thus I get the following error message when executing the cell ...
2
votes
1answer
146 views
Nested Sums to multiple sum
I would like to automatically "move nested sums to the left". I mean, just take out of an expression all the summations and go from a nested Sum to a multiple sum. Something like starting with:
...
2
votes
1answer
185 views
Integral not simplifying
I specify a function in terms of an integral and then try to evaluate it with Simplify. However, the answer is not really simplified to what it should be.
...
2
votes
1answer
56 views
Differentiating with respect to vectors of unspecified length
Given a function defined by
f[x_,y_] := Sum[ x[[i]] (g[y[[i]]] - g[Total[y]] - Log[x[[i]]]), {i, 1, Length[x]}]
I can easily calculate the derivative for a fixed ...
2
votes
1answer
118 views
Variable name string to expression
I'm not sure how to name this problem appropriately. But anyway.
I have, say, three variables (arrays in my case), which I call:
A1, A2, A3
I would like to ...
2
votes
1answer
198 views
How can I solve an exponential inequality in Mathematica?
I would like to solve the equation:
A Exp[m t + s Sqrt[t] x - 1/2 s^2 t] >= K
with respect to x (which is in the exponent) ...
2
votes
1answer
216 views
Reduce/Solve an equation with symbols in powers
I am trying to solve the following equation with respect to x.
eqn = x^z + y == a;
But when I do
...
2
votes
0answers
61 views
Reducing exponential inequalities fails
I am quite stumped by this problem :
Reduce[ N^(x-y) <1 && N > 0 , x, Reals]
gives the expected result
...
2
votes
1answer
130 views
Can I reduce a matrix inequality such as $\mathbf x^\prime\mathbf A\mathbf x > \mathbf x^\prime\mathbf x$?
I'm new to Mathematica. When I do linear algebra, I wonder if I can have an inequality such as $\mathbf x^\prime\mathbf A\mathbf x > \mathbf x^\prime\mathbf x$, where $\mathbf x$ is a column vector ...
2
votes
0answers
163 views
Numerical-Symbolical Integration (Calculus)
I created a simple numeric-symbolic integration. Here you can use symbolical and numerical techniques at the same time. You can also interpolate numerical integrals.
The problem with my function is ...
1
vote
2answers
143 views
Write a function that returns the logarithmic derivative
How can we write a function that if we input an expression f, it returns the log derivative $\frac{1}{f} \frac{df}{dx}$. We have to use a conditional or pattern test so that the function accepts any ...
1
vote
1answer
102 views
Improve performance for finding Fibonacci number which have divisibility property
In this post, the OP requires finding a Fibonacci number having some divisibility property with Mathematica and Maxima. I tired tried that Mathematica code on Mathematica 9.0 and it's still slow ...
1
vote
1answer
75 views
Why is a non-convergent series simplified to zero?
Sum[Sin[n*x]*Sin[n] /. x -> 1, {n, 1, Infinity}] ==
Sum[Sin[n*x]*Sin[n], {n, 1, Infinity}] /. x -> 1
Sum::div: Sum does not converge. >>
...
1
vote
2answers
179 views
Symbolically associate vectors and their norms
I am wondering how to handle the following situation: I do have vectors of known dimension that I would like to handle symbolically. I suppose I can do something like
...
1
vote
1answer
69 views
Generating a list of symbolic coefficients [duplicate]
I am trying to do something which I assume should be very simple: I want to generate a list with symbolic coefficients that looks like this:
...
1
vote
1answer
60 views
Only perform a symbolic differentiation once
I want to define a function that involves a differentiation step that Mathematica can do easily, which might be of the form
...
1
vote
1answer
151 views
Symbolic calculation
Is there any software where this kind of symbolic calculation is possible?
s = 0
for i = 1 to m
j = 2 i + a - t
if (j > 0) s = s + a
I want s as a ...
1
vote
0answers
58 views
Symbolic Integration of Boole [closed]
Why is
Integrate[Boole[x < 1], q]
resulting in
Piecewise[{{x, x <= 1}}, 1]
I'd expect
...
1
vote
1answer
126 views
Functions that operate on symbolic matrices?
I'd like to write functions that operate on symbolic matrices, and do nothing when fed anything else.
...
1
vote
0answers
143 views
What's a good data structure to represent a, b, a and b, a or b? [closed]
I have a function foobar[x_] that can produce 4 types of output
a
b
a or b
a and b
What's a good data structure, or better ...
0
votes
1answer
144 views
0
votes
1answer
196 views
How to define a derivative/Variation operation in Mathematica from scratch
I am looking for a method in Mathematica 8 to define my own derivative/variation (independent of built-in operations). I do not want to re-define built-in objects since I fear that this could cause ...
0
votes
1answer
87 views
Alleviating a bottleneck involving a function call with symbolic derivatives
I have a bottleneck problem involving a function call with symbolic derivatives.
I don't have much experience with Mathematica (or any dynamic language) and I'm certain that the way I've set this up ...
0
votes
1answer
117 views
Industrial Level Applications. Recipe for mixed notation of equations set
I am working with large (linear) equations set within Mathematica in numerical notation. For example, set from 4056 eq. is solved for a second, no more. There is no doubt, result is great. But even ...
0
votes
2answers
73 views
Dropping Higher Order Terms in symbolic evaluation
I have a series of symbolic manipulations (along with some coefficients).
As a sample, here is one of the intermediate forms
...
0
votes
0answers
18 views
Symbolic Calculations with formal matrices [duplicate]
I want to make calculations with matrices in the form (for lovers of statistical mechanics, is just the first step replica symmetry breaking)
...
-1
votes
3answers
198 views
Sqrt — how to get negative branch?
One of the many attractions of Mathematica is that integers are generally treated as exact symbolic entities, and not just as numbers. I was just playing with Sqrt, and was puzzled by what appeared to ...
