Questions tagged [difference-equations]
Tag for the usage of RSolve, RecurrenceTable, DifferenceRoot, and other functions related to difference equations.
215
questions
3
votes
4answers
70 views
RecurrenceTable for systems of linear difference equations
I'm working on a project that involves developing a financial forecasting model. The equations used in the model will largely be linear difference equations (estimated via some form of regression ...
2
votes
0answers
29 views
RecurrenceTable doesn't evaluate with constant right-hand side
One of my functions automatically generates systems for RecurrenceTable. Usually works fine, but today I encountered a problem. If the right-hand side is a ...
0
votes
0answers
43 views
Help with “Coordinate should be a pair of numbers, or a Scaled or Offset form.”
I am plotting the pair of recurrence relations:
...
3
votes
0answers
28 views
RSolve produces a solution which is not complete?
Consider the following solution of a recurrence relation in two variables
RSolve[f[x + 1, y] == f[x, y + 1], f[x, y], {x, y}]
{{f[x, y] -> C[1][x + y]}}
It ...
1
vote
0answers
23 views
Issue plotting a system of recurrence equations
Mathematica noob issues here. So I've got a system of recurrence equations, and following suggestions in other posts,(Plotting two recursive functions) I have the following:
...
1
vote
1answer
57 views
Solving a recurrence relation with constraints
I have the following recurrence relation with complex coefficients:
c[n] == Sqrt[n-1] c[n-1] + Sqrt[n] c[n+1]
I also have the constraint that
$\sum_n |c_n|^2 = ...
5
votes
1answer
91 views
Solving partial recurrence equation with several recurrence indices
I'm trying to solve a recurrence relation for a function of three variables. It works with 2 variables but not with 3.
A simple example is:
...
1
vote
1answer
38 views
Problem when using NMinimize in a RecurrenceTable
I have a problem when I'm trying to use NMinimize in my RecurrenceTable, like in this example :
...
4
votes
3answers
417 views
Slow computation of recursive sequences
I want to investigate the asymptotic behavior of the following recursive system:
...
3
votes
2answers
62 views
What is the fastest way to calculate series from recurrence solutions with no closed form?
I am not very experienced with Mathematica. I want to calculate the series from recurrence solutions. These solutions have no closed-form. I want to improve the approximation and hence need a good ...
1
vote
1answer
60 views
recurrence equation
The output of Mathematica is only a copy of the input. What am I doing wrong?
...
1
vote
0answers
37 views
How to specify an element of a list when using RecurrenceTable
My problem is that I'm trying to get a list of refraction angles in a multilayer structure (for the sake of this example - with two types of refraction indices and eleven layers of them). The code is ...
1
vote
0answers
55 views
Computing a system of ordinary differential equations with initial condictions over a continuous range [closed]
I have some questions about Mathematica programming and would appreciate if you could help me.
I want to solve a system of ordinary differential equations μ '[t] ...
0
votes
0answers
21 views
Does Mathematica find most general recurrence solutions?
Consider e.g. the following recurrence relation solution:
RSolve[a[m, n + 1] == a[m + 1, n], a[m, n], {m, n}]
{{a[m, n] -> C[1][m + n]}}
which states that the ...
1
vote
0answers
35 views
Problems with the parametric Recurrence Table
I am trying to construct a minimization program where I have to minimize a function with respect to a matrix. This matrix enters into the optimization program in a convoluted manner together with data....
0
votes
0answers
37 views
How to find the value in which an expression becomes greater than another
I have the following expressions:
$\Delta \sigma_1=\frac{2 \gamma ^2 \left(\text{$\sigma $Y} \log \left(\frac{\gamma }{\alpha }\right)+\text{pe}\right)}{\left(\gamma ^2-1\right) \rho ^2}$
$\Delta \...
0
votes
0answers
26 views
Lyapunov exponents of discrete dynamics with two parameters in one dimension
How can we calculate if we have discrete dynamics with two parameters:
f[x_, a_, b_] := Piecewise[{
{1 - a*x, x <= 1/2},
{1 - b*x, x > 1/2}
}]
0
votes
0answers
47 views
Bifurcation diagram with two parameters [duplicate]
I have a question. In Bifurcation diagram of a difference equation I asked for one parameter. And now I am going to tell how do I make a bifurcation diagram of that function with two parameters? I ...
1
vote
2answers
166 views
Bifurcation diagram of a difference equation
The function is
f[x_, a_] := Piecewise[{{x (1 + a - a*x), x <= 1/2}, {x (1 - a + a*x), x > 1/2}}]
How to make the bifurcation graphic of it?
What ...
0
votes
2answers
78 views
Solving recurrence equation with variable $x$
Please I want to solve this recurrence equation
$$p_n(x)=\frac{1}{x}\left[\frac{n\;}{\sqrt{2 n-1} \sqrt{2 n+1}}p_{n-1}(x)+\frac{(n+1)}{\sqrt{2 n+1} \sqrt{2 n+3}}p_{n+1}(x)\right]$$
$x$ is a variable
...
0
votes
1answer
79 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') - ...
1
vote
1answer
72 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
176 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
60 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
30 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
24 views
0
votes
1answer
41 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
94 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
32 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
57 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
96 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
94 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
103 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
178 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
76 views
Spectrum of eigen values for coupled differential equations
How do I obtain a spectrum of eigenvalues for my system of coupled differential equations?
$$
kf''(\theta) + \epsilon_{1} f(\theta) + a\cos(b \theta + c) g(\theta) = \lambda f(\theta),\\
a\cos(b \...
0
votes
0answers
69 views
Solving a system of recurrence equations
Can anybody help me with the following code for solving a system of nonlinear recurrence equations. When I evaluate the kernel and run it, the output is the same is my input as if the Mathematica is ...
0
votes
0answers
45 views
Recurrence Relation based on Vectors
I am new to Mathematica.
I try to solve a recurrence relation based on vectors.
So a[n] is a vector for all n (as well as ...
1
vote
0answers
112 views
Solving a recurrence relation with variable coefficients
I am trying to solve this recurrence inequality for $ a_n $, hopefully in terms of $ a_0，a_1，c $ and $ x $,
$$(1-x)a_{n+1} \le xa_n + (1+x)a_{n-1} + c\quad\forall\ n\ge1$$
What I tried: RSolve. But ...
1
vote
0answers
43 views
Why does RSolve not give what I expect?
I have a model based on a digraph G. I construct a system of difference equations, modelFull, as seen below.
...
0
votes
0answers
61 views
Avoid Recursion in lag and difference operations
I have a panel data situation and I'm interested in taking lags and differences and using Mathematica to simplify the algebra of the result.
Currently I'm working with a model like this:
...
-1
votes
1answer
83 views
How can I solve this systems of differential equation and show a plot?
$$ \frac{\mathrm du}{\mathrm dt} = 1 - u \mathrm e^{\epsilon(8q-1)} $$
$$ \frac{\mathrm dq}{\mathrm dt} = u \mathrm e^{\epsilon (q-1)} - q $$
$ 0 \leq \epsilon \leq 0.1 $
$u(0) = 0$ and $ q(0)=0$
...
0
votes
0answers
38 views
Residues of products
i have the following problem:
My function is given by:
$(cz^{-1}+aq^{-j}-bq^{-2j}z)\prod_{m=1}^{Q-1}\frac{qz-z_{m}}{z-z_m}+(-cz^{-1}+dq^{j}+bq^{2j}z)\prod_{m=1}^{Q-1}\frac{q^{-1}z-z_{m}}{z-z_m}=E$,
...
0
votes
1answer
44 views
fisrt 5th iterations of a sequence of functions: integro-differential equations [closed]
Please I am struggling to compute with mathematica the first 5th iterations of the sequence of functions $u[n,t]$ satisfying the integro-differential equation
Please help me with the code.
Patrick
2
votes
1answer
176 views
Using NIntegrate in Finite Difference Derivative method
I'm trying to solve a second order differential equation using the code given by @xzczd here which is based on this.
What this ...
1
vote
0answers
81 views
Zeros of a rational fraction sequence
This is a follow-up of the question Finding a function/differential equation from a 2nd order recurrence relation, I asked yesterday. The reason why I didn't edit the original question was that in ...
2
votes
1answer
74 views
Finding a function/differential equation from a 2nd order recurrence relation
Consider the following 2nd order recurrence relation:
$$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
90 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
214 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:
$12 \rightarrow (1^3 + 2^3) = 9$...
