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Matthew Hunt


Last seen: 1 year ago |  Active since 2018

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I am trying to solve a pair of coupled linear PDEs using backward Euler and Newton-Raphson
I am tring to solve a coupled pair of 1D PDEs in time and space using the backward Euler and Newton-Raphson. One of them is a hy...

1 year ago | 1 answer | 0

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Question


Can I include an ODE when I solve a system of PDEs in pdepe
Suppose I have a moving boundary problem and I have an ODE governing the length of the bounary I am interest in. Is it possible ...

1 year ago | 1 answer | 0

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Question


Code has numerical issues that I don't understand
I managed to get a system of PDEs down to a large system of ODEs via the method of lines. I managed to code it up using ode45 bu...

1 year ago | 0 answers | 0

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Question


How do you include a mass matrix in ode45?
ode45 solves a set of equations The length of is 3N+1, I have a non identity mass matrix M, but I've not seen any real ins...

1 year ago | 2 answers | 0

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User defined function within ode45
I have the following ODE system: If f(t) is a constant, then I can easily write the code, but I have f(t) as a piecewise ...

1 year ago | 2 answers | 0

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Can I get a better fit to data
I've written a code to find some parameters to a mathematical model but I can't seem to get a good fit to the experimental data....

2 years ago | 1 answer | 0

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Use of fmincon with objective function as m-file
I am finding parameters for a model. I thought the best thing was to define the objective function that I wiah to minimise as f...

2 years ago | 2 answers | 0

2

answers

Question


Can we get functions from the curve fitting toolbox?
I am using the curve fitting toolbox and I have some data that I want to create a function from. I am using a spline function to...

2 years ago | 2 answers | 0

2

answers

Question


Solving PDEs with mixed derivatives
Suppose I have an equation of the form: Can I use pdepe to solve that equation as is, or do I have to do a co-ordinate tran...

2 years ago | 1 answer | 0

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Answered
Implementing Crank Nicholson in spherical setting
Question resolved.

2 years ago | 0

| accepted

Question


Implementing Crank Nicholson in spherical setting
I am trying to solve the spherical diffusion equation using the Crank-Nicholson method. I think that I understand the method, I ...

2 years ago | 3 answers | 0

3

answers

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Code doesn't terminate in the way that I want
I have a loop which changes the value of a vector at each iteration of the loop. I don't want the values in the loop to get grea...

2 years ago | 1 answer | 0

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My implemetation for Newton's method doesn't seem to be working
My goal is to solve the following set of nonlinear equations: for this I use the Newton method in the form: The code t...

3 years ago | 1 answer | 0

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answer

Question


I want to do a 1D integral of some 2D data
Suppose I have a function which is defined as some numerical data which is equally spaced and I wish to compute: How would I...

3 years ago | 2 answers | 0

2

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Question


Speeding up pdepe calculation
I have a pdepe bit of code I want to speed up if I can. I have a (typically) 400x800 array as a source term, the code I'm curren...

4 years ago | 0 answers | 0

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Importing a two variable function into pdepe
Hi I want to solve a diffustion pde I understand how to do this if Q is a single variable function using interp1, but I do...

4 years ago | 1 answer | 0

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Empirical source terms with PDEPE
Suppose I'm solving an equation: ...

4 years ago | 1 answer | 0

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How do I include a user specified hessian function for fmincon?
I am working on an optimisation code and I have a Hessian function I wish fmincon to use. I'm currently having trouble trying to...

4 years ago | 1 answer | 0

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Answered
Is it possible to store the intermediate values of fmincon?
So I had to do a lot of searching and turns out that this is possible without downloading code. The key was to use 'OutputFcn' i...

4 years ago | 1

| accepted

Question


Is it possible to store the intermediate values of fmincon?
If I'm runnning fmincon, and I want to see the values of the parameters at each iteration, is there a way to do this? The docum...

4 years ago | 5 answers | 0

5

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Question


Defining a stopping criterion for fmincon
I am looking at an optimisation problem with the following objective function: ...

4 years ago | 1 answer | 0

1

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Objective function doesn't converge but jumps around
I have been trying to complete an optimisation problem. I am looking at radial heat diffusion on a cylinder. I want to tackle it...

4 years ago | 0 answers | 0

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Crank Nicholson method for cylindrical co-ordinates
I am trying to solve the heat equation in cylindrical co-ordinates using the Crank-Nicholson method, the basic equation along wi...

5 years ago | 0 answers | 0

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Converting anonymous function to a matrix
I have a function of the form: , which I want to evaluate. I could do this old school with a double loop but that would take t...

5 years ago | 1 answer | 0

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Diagonal matrices with spdiags
I'm working on a numerical solution to an equation and as part of this I have to solve a matrix solution. The system of equation...

5 years ago | 1 answer | 0

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Is there a way of removing these for loops to speed up my code?
I have the analytical solution to the following PDE: with boundary condition and and initial condition in the form of a Gr...

5 years ago | 1 answer | 0

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I have: Error using bsxfun Non-singleton dimensions of the two input arrays must match each other.
So I have some code which I want to get working and I don't understand the error which is being given to me which is: Error usin...

5 years ago | 2 answers | 0

2

answers

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Interp1 returns NaN for a value
I have some data (x,f(x)) where 0<=x<=1 and I have N points. I wish to obtain f for an inteverval [a,b] which is well within the...

5 years ago | 1 answer | 1

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answer

Question


Tracking the size of a variable
Hi, I have a vector of length 200. When I run my program it somehow halfs in length, and I have no idea why. Is there a way of ...

5 years ago | 1 answer | 0

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Answered
Not enough input arguments when doing global optinisation
I've seen what I need to do. The set up of the function is different to lsqcurvefit: I had to define the function as: fun = ...

6 years ago | 0

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