Community Profile

# Josh Meyer

### MathWorks

129 total contributions since 2013

I write MATLAB Math documentation

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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...

4 mesi 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...

4 mesi 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...

4 mesi 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...

4 mesi 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 ...

4 mesi 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 ...

6 mesi 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. ...

7 mesi 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...

7 mesi ago | 0

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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....

9 mesi ago | 0

| accepted

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...

10 mesi 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 ...

10 mesi 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...

11 mesi 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 ...

11 mesi 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...

11 mesi 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...

oltre un anno 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...

oltre un anno 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...

oltre un anno 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 ...

circa 2 anni 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...

circa 2 anni 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...

oltre 2 anni 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...

oltre 2 anni 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...

oltre 2 anni ago | 2

| accepted

2nd order numerical differential equation system solving
Use the Symbolic Math Toolbox function <http://www.mathworks.com/help/symbolic/odefunction.html |odeFunction|> to convert the |o...

oltre 2 anni ago | 0

I am looking for a way to share the output of my event function with the main function used by the ode solver.
If you specify a terminal event in the event function, then the integration will halt when the event occurs. You can then use th...

oltre 2 anni ago | 0

| accepted

May you help me please to continue my syytem seconder order DE function?
Since you have boundary conditions you'll want to use bvp4c or bvp5c. See <https://www.mathworks.com/help/matlab/math/boundary-v...

oltre 2 anni ago | 0

Dynamics of Vibro-Impact system with impact condition
If you use |ode45| then a chunk of your code becomes moot - you just need the initial conditions |y0| and time span |[t0 tfinal]...

oltre 2 anni ago | 0

Event function in ode45
My guess is you are using the "old" way to pass parameters to the ODE function F, where they are specified as trailing input arg...

oltre 2 anni ago | 1

How do I speed up ODE15s?
Some things to try... # For stiff problems you should always specify the Jacobian or its sparsity pattern via the options str...

oltre 2 anni ago | 2

| accepted