Questions tagged [difference-equations]
Tag for the usage of RSolve, RecurrenceTable, DifferenceRoot, and other functions related to difference equations.
195
questions
0
votes
1answer
75 views
How to get solutions for recursive relations using RSolve?
I have
$$a(x,t+2) - a(x,t) = -\cos{\theta} [a(x+1,t+1) + a(x-1,t+1)]$$
Setting $t' = -t\cos(\theta)$ fetches under the continuum approximation $$2 \frac{\partial a(x,t')}{\partial t'} = a(x-1,t') - ...
2
votes
1answer
63 views
Problem with RSolve function
When I use RSolve to solve the recurrence: $S(n)=\dfrac{1}{-S(n-1)-2},S(1)=-2/3$, it gives an empty solution:
however the solution should be:$S(n)=-\dfrac{n+1}{n+2}$
Did I do something wrong?
6
votes
2answers
153 views
Find a stable 3-cycle of the sine map
I am trying to find an stable 3-cycle for the sine map $g(x) = a \sin(\pi x)$ but I do not know exactly how to use mathematica to do so. Is there anyone familiar with this?
$x$ lies as before ...
-1
votes
1answer
51 views
Error when Solving Recurrence Relation
I would like to analyze the following recurrence relation.
$r_i = r_{i-1} - \frac{1}{2} \cdot \sqrt{1 - \frac{4\pi^2\cdot r_{i-1}^2}{n^2}}$
$r_0 = \frac{n}{2\pi}$
I have implemented this as ...
0
votes
0answers
86 views
Is it possible to find the Rössler attractor using only a set of Lyapunov exponents?
Is it possible to use a set of Lyapunov exponents to determine the orbits of the Rössler system? If so, could how would I go about plotting them?
EG.
Known
Unknown
0
votes
0answers
27 views
Trying to solve recursion using rsolve
I'm new to Mathematica, and I'm trying to use RSolve to solve an equation I couldn't do in Matlab, as I got errors there too. This is the system I'm trying to solve:...
0
votes
0answers
21 views
0
votes
1answer
39 views
Help with recurrence relation
I try to solve the following recursion for $n \in \mathbb{N}$.
$r_i = r_{i-1} - \frac{1}{2} \cdot \sqrt{1 - \frac{4\pi^2\cdot r_{i-1}^2}{n^2} \cdot \cos^2 \left(\frac{\pi}{n}\right)}$
$r_0 = \...
1
vote
1answer
83 views
Solving recursive equations with RSolve, with constraint and subscripts
I'm trying to solve this set of equations in generality, where $n$ can vary.
$\begin{align*}
P_{1}&=1-\sum_{i=2}^{n}P_{i}\\
P_{i}&=\frac{c_{i-1}P_{i-1}}{c_{i}+\mu_{i}}, \quad i=2,\dots,n-1\\
...
0
votes
0answers
29 views
Generating DifferenceRoot Equation
I like to find a difference root equation I use the following methods use for mathematica but I have not get any result
Clear[p]
...
0
votes
0answers
23 views
some errors the DiferenceRootReduce
I try to calculate
DifferenceRootReduce[(
Sqrt[\[Pi]]
Gamma[3/2 + k] HypergeometricPFQ[{3/2 + k, -n}, {2 + k}, p])/
Gamma[2 + k], k]
but any result
...
2
votes
3answers
49 views
Using rule output as function
Im trying to define a function using the output from RSolve, however i cant get it to work properly.
I have a RSolve that output something like:
...
1
vote
1answer
73 views
RSolve and a Piecewise Recurrence + Runtime
This should really be a comment to this answer but I don't have enough rep. I'd like to know how to do the same thing (efficiently - see below) but with $\mod 3$ conditions, i.e. define a[k] to be the ...
1
vote
1answer
40 views
RSolve for three arguments
I would like to find the general expression for a recursive equation:
...
0
votes
1answer
61 views
Recurrence Relation with two variables and boundary conditions
I try to express the following recurrence relation in Mathematica:
I am very sorry but for any reason I am not allowed to embed math code here...
\begin{align*}
x_{1,t} &= \frac{1}{2} x_{1,t-...
1
vote
1answer
86 views
Solution of differential equation and then draw a graph
I have two differential equations:
$da/dt = a (.3 a^{-3} + .7)^{1/2}$ and $d \tau /dt = 1/a$. The initial conditions are $t = 0$; $a = 1$ and $\tau = 0$, respectively.
How can I solve the ...
4
votes
2answers
142 views
RSolve not reducing for a certain recurrence relation
I'm trying to use RSolve as follows to solve a recurrence relation:
...
3
votes
1answer
65 views
Spectrum of eigen values for coupled differential equations
How do I obtain a spectrum of eigenvalues for my system of coupled differential equations?
$$
kf''(\theta) + \epsilon_{1} f(\theta) + a\cos(b \theta + c) g(\theta) = \lambda f(\theta),\\
a\cos(b \...
0
votes
0answers
53 views
Solving a system of recurrence equations
Can anybody help me with the following code for solving a system of nonlinear recurrence equations. When I evaluate the kernel and run it, the output is the same is my input as if the Mathematica is ...
0
votes
0answers
38 views
Recurrence Relation based on Vectors
I am new to Mathematica.
I try to solve a recurrence relation based on vectors.
So a[n] is a vector for all n (as well as ...
1
vote
0answers
89 views
Solving a recurrence relation with variable coefficients
I am trying to solve this recurrence inequality for $ a_n $, hopefully in terms of $ a_0，a_1，c $ and $ x $,
$$(1-x)a_{n+1} \le xa_n + (1+x)a_{n-1} + c\quad\forall\ n\ge1$$
What I tried: RSolve. But ...
1
vote
0answers
40 views
Why does RSolve not give what I expect?
I have a model based on a digraph G. I construct a system of difference equations, modelFull, as seen below.
...
0
votes
0answers
35 views
Avoid Recursion in lag and difference operations
I have a panel data situation and I'm interested in taking lags and differences and using Mathematica to simplify the algebra of the result.
Currently I'm working with a model like this:
...
-1
votes
1answer
81 views
How can I solve this systems of differential equation and show a plot?
$$ \frac{\mathrm du}{\mathrm dt} = 1 - u \mathrm e^{\epsilon(8q-1)} $$
$$ \frac{\mathrm dq}{\mathrm dt} = u \mathrm e^{\epsilon (q-1)} - q $$
$ 0 \leq \epsilon \leq 0.1 $
$u(0) = 0$ and $ q(0)=0$
...
0
votes
0answers
36 views
Residues of products
i have the following problem:
My function is given by:
$(cz^{-1}+aq^{-j}-bq^{-2j}z)\prod_{m=1}^{Q-1}\frac{qz-z_{m}}{z-z_m}+(-cz^{-1}+dq^{j}+bq^{2j}z)\prod_{m=1}^{Q-1}\frac{q^{-1}z-z_{m}}{z-z_m}=E$,
...
0
votes
1answer
39 views
fisrt 5th iterations of a sequence of functions: integro-differential equations [closed]
Please I am struggling to compute with mathematica the first 5th iterations of the sequence of functions $u[n,t]$ satisfying the integro-differential equation
Please help me with the code.
Patrick
2
votes
1answer
152 views
Using NIntegrate in Finite Difference Derivative method
I'm trying to solve a second order differential equation using the code given by @xzczd here which is based on this.
What this ...
1
vote
0answers
79 views
Zeros of a rational fraction sequence
This is a follow-up of the question Finding a function/differential equation from a 2nd order recurrence relation, I asked yesterday. The reason why I didn't edit the original question was that in ...
2
votes
1answer
72 views
Finding a function/differential equation from a 2nd order recurrence relation
Consider the following 2nd order recurrence relation:
$$A_{1}=1,\; A_{2}=z$$
$$A_{n+2}(z)=(b_n+z)A_{n+1}(z)+a_nA_{n}(z),\; n=1,2,3,...$$
where,
$$b_n=n\left(n+m+\frac{1}{2}\right),\; a_n=k^2n\left(...
1
vote
1answer
80 views
How to generate a series with recurrence relation? [closed]
I am a beginner in Mathematica and stuck on a problem.
I want to generate a series using a recurrence relation, however, I am facing the problem while feeding previous values.
...
8
votes
3answers
210 views
Using Total inside the RecurrenceTable
I would like to perform an operation over IntegerDigits recurrently.
The operation is the sum of cubes of the digits, for example:
$12 \rightarrow (1^3 + 2^3) = 9$...
2
votes
0answers
121 views
DSolve analytical solution of the system equation with two variable
I have a difficulty to solve this system equations:
...
3
votes
1answer
119 views
Second order 1D equation with integral boundary condition
Is it possible to solve below equation in Mathematica in range $0<x<r$?
$f''[x] + \frac{2f'[x]}{x} = -A e^{-B f[x]}$
$ f'[x]|_{x=r}=-\alpha\:\:\:\:\:$ and $\:\:\:\int_0^r f(x) x^2 dx= \gamma$
...
1
vote
0answers
45 views
How to interpret RSolve solution with negative factorial?
I'm having trouble interpreting the following result of RSolve to this difference equation:
...
5
votes
3answers
110 views
How to find a list of values of recurrence equation?
I tried with RSolve,but it fails:
RSolve[{x[n + 1] == n + Sum[j*x[j], {j, 1, n}], x[1] == 1}, x[n], n]
Returns unevaluated ...
0
votes
0answers
61 views
DifferenceRoot help
I have being calculate some Series Coefficient and the result was and DifferenceRoot equation but i do not how
...
0
votes
1answer
88 views
Solving recurrence relations
I have the following recurrence system:
$$\pi_0 =.25\pi_0 + .25q\pi_1+.5q\pi_2 + q\pi_3 $$ $$\pi_1 =.25\pi_0 + .25q\pi_1+.5\pi_2 + p\pi_3 $$ $$\pi_2 =.25\pi_0 + .25p\pi_1+.5p\pi_2
+ 0 $$ $$\pi_3 =....
2
votes
1answer
156 views
Guessing recursion in rational functions
I want to know if there is a package in Mathematica that can give back some recursion given a list of polynomial in $f_{n}(h)$. For example I know there exists package RISC guess that where I give ...
0
votes
0answers
80 views
Solving a boundary-value recurrence relation
I would like to solve a recurrence relation of the form
...
0
votes
0answers
47 views
How many solutions are there in this equation $u_{2018}=0$?
I have a sequence $(u_n)$ so that $u_1=a$ and $u_{n+1}=4u_n (1-u_n)$, for all $n=1,2,\ldots$. How many solutions are there in this equation $u_{2018}=0$?
I tried
...
0
votes
0answers
45 views
RSolveValue syntax
Can't see anything wrong with this:
sol4 = RSolveValue[{a[n + 1] - 1.2*a[n]*(1 - a[n]) == 0, a[1] ==0.1},
a[n], n]
But I just get an echo from Mathematica
3
votes
2answers
88 views
Vector and matrix use in RecurrenceTable
Why is this code snippet that uses matrix and vector elements work?
...
2
votes
1answer
70 views
Recurrence table doesn't like non-linearity?
When I evaluate the following RecurrenceTable expression
...
0
votes
1answer
69 views
Determining the distribution and other characteristics of a variable defined by a recurrence relation
I want to determine the distribution and some other characteristics of a recursive defined variable and need hereby some help/advice.
I have the recurrence relation
$\qquad X_t = X_{t-1} + \phi (\...
0
votes
1answer
78 views
Sequence equivalent research
I'm studying this series:
I know that there is this relation:
($\ell$ is the common limit of the two series)
Do you know a Mathematica function that could prove this relation?
0
votes
1answer
46 views
RecurrenceTable with defined functions
I am trying to solve a difference equation using RecurrenceTable as follows.
...
0
votes
2answers
142 views
Solving difference equations involving transcendental functions
v = 0
Solve[Tan[Sqrt[ϵ]]/Sqrt[ϵ] == -Tan[Sqrt[ϵ - v]]/Sqrt[ϵ - v], ϵ]
Solve[Tan[Sqrt[a]]/Sqrt[a] == -Tanh[Sqrt[v - a]]/Sqrt[v - a], a]
I want to evaluate ...
0
votes
2answers
165 views
Why does this partial differential solution not work?
Here I am trying to solve a simple partial differential equation i.e. $ \frac{\partial^2f}{\partial x^2}+\frac{\partial^2f}{\partial y^2}=6y
$ but for some reason it won't solve it. There clearly is a ...
0
votes
1answer
122 views
periodic point of a quadratic map
I am analyzing a discrete dynamic quadratic map. The bifurcation diagram shows the existence of an asymptotic 3- cycle periodic point for a given parameter. But the graphic of the lyapunov exponent ...
0
votes
0answers
53 views
how to To specify initial conditions for a system of ode?
I have the following system of ode:
a = {{-3, 1}, {-1, -5}}; eqns =
Thread[{y1'[x], y2'[x]} == a.{y1[x], y2[x]} + {1, 1}];
I solved the general solution for a system of ode. However, I cannot ...
