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# Josh Meyer

### MathWorks

135 total contributions since 2013

I write MATLAB Math documentation

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Where can I get a samaritan to help me with my code of a Reaction–Diffusion Delayed Neural Networks
You should be able to use pdepe. Just calculate tau in the pdefun function and pass the delayed time value when you call the sub...

21 jours ago | 0

Boundary conditions for a ring PDE
pdepe does not allow for time derivatives in the boundary conditions. The boundary conditions are expressed in terms of the flux...

21 jours ago | 0

how i can solve the following PDE using periodic boundry coditions
Periodic boundary conditions require that when something leaves one boundary with a certain velocity, it enters the boundary on ...

21 jours ago | 0

| accepted

PDEPE: How to set I.C as a variable?
pdepe has expectations for the initial condition function. Namely, that it will use the functional signature: function u0 = icf...

21 jours ago | 0

Writing PDE boundary conditions
pdepe expects the boundary conditions to be written in a standardized form: Notice that only p can depend on the variable bei...

21 jours ago | 0

What is the “pdentrp” function in the “pdepe” function?
This is an internal, private helper function, so it does not have documentation beyond help text. You can access the file with t...

21 jours ago | 0

Retaining the max value during scattered data interpolation
You'll need to do this manually before calling scatteredInterpolant. There are a few ways to do it, you could use a logical mask...

5 mois ago | 0

| accepted

PCG and MINRES question
Since A*x = b, the sizes of the variables must be: A * x = b (M-by-N) * (N-by-1) = (M-by-1) But since alm...

5 mois ago | 0

Getting the intermediate solutions in an iterative solver
While the functions themselves don't return intermediate results, consider that the resvec output of all the iterative solvers r...

5 mois ago | 0

why convergence is not happening in pcg function ?
There are two things to notice here: In the first message you printed where PCG converges after 1 iteration, this is an indicat...

5 mois ago | 0

PCG on a large sparse matrix from Finite difference method
Yes, you can provide the coefficient matrix as a function handle instead of a numeric matrix. This is because PCG, like many of ...

5 mois ago | 0

Best integration method to integrate this oscilating function
integral can handle oscillatory integrands as long as there aren't too many oscillations, and you supply plenty of WayPoints in ...

8 mois ago | 0

Processing Data in a Tall Array
findgroups and splitapply work with tall arrays, so don't worry about using tall.transform or tall.reduce for this simple task. ...

8 mois ago | 0

How does integral2 work?
The basic principle of numeric integration is you are calculating the area under the curve by splitting it up into smaller piece...

8 mois ago | 0

| accepted

Problem with boundary conditions for PDEPE
From the doc for pdepe, "When m > 0 and a = 0, boundedness of the solution near x = 0 requires that the flux f vanish at a = 0....

10 mois ago | 0

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what's the difference in accuracy between solving a stiff problem by ode15s and ode45?
Stiffness is more of an issue of stability than accuracy. Nonstiff solvers can solve stiff problems, it just takes them a long t...

11 mois ago | 0

Change font size of node name in a graph
Several new properties were added to GraphPlot objects in R2018b to enable customization of node and edge labels. In particular ...

11 mois ago | 1

| accepted

Problems with pdepe with disconnected variables in c, f and s
c, f, and s are expected to be column vectors with length equal to the number of equations being solved. Since you have 1 equati...

12 mois ago | 1

| accepted

Implementing boundary condition in pdepe
The form for the boundary conditions expected by the solver is Since you have a system of two equations, each p and q should ...

environ un an ago | 0

pdepe help! (boundry condition in PDE solver)
Your boundary condition function includes the line pl = ul-TT(i); TT(i) is not defined within view of the function, so that i...

environ un an ago | 1

| accepted

Submitted

Plotting the Binomial Coefficient
Live script that plots the binomial coefficient over all positive and negative argument combos.

Solved

Project Euler: Problem 2, Sum of even Fibonacci
Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 te...

plus d'un an ago

Solved

Triangle sequence
A sequence of triangles is constructed in the following way: 1) the first triangle is Pythagoras' 3-4-5 triangle 2) the s...

plus d'un an ago

Solved

Find a Pythagorean triple
Given four different positive numbers, a, b, c and d, provided in increasing order: a < b < c < d, find if any three of them com...

plus d'un an ago

'Undefined Function or Variable' Error when Function is Defined
Looks like the issue is you define cp in the workspace and the function can't access that variable when it gets called. So, try ...

plus de 2 ans ago | 0

| accepted

Use griddata ignoring gaps in data
To interpolate without the gaps you need to remove them from the data before interpolating, request values on the full grid (inc...

plus de 2 ans ago | 1

| accepted

system of 1st and 2nd order differential equations ode45
The documentation explains how to express higher-order equations as first-order equations: <https://www.mathworks.com/help/matl...

plus de 2 ans ago | 0

Solving coupled differential equations
The immediate problem is that you provide too many output arguments to ode45. The components of y will be returned as columns if...

plus de 2 ans ago | 0

| accepted

Commands related to big data and tall array to annalyze data from .csv files.
Check out the documentation: <http://www.mathworks.com/help/matlab/tall-arrays.html Tall Arrays> The general procedure is tha...

plus de 2 ans ago | 2

| accepted