Question

Choosing more stringent values for RelTol and AbsTol in ode45, for smooth functions such as sin(t) or cos(t), does not change the numerical solutions,

Hi, I'm playing with the RelTol and AbsTol options for the ode45 solver, choosing more stringent values such as 1e-10 for bo...

3 months ago | 0 answers | 0

Question

How does choosing more stringent RelTol and AbsTol values in ode45 compare with choosing finer tspan integration time-steps?

Hi, So I modified my ode45 error tolerances, both RelTol and AbsTol, to be at 1e-10. 1e-14 or so seems to be the most strin...

3 months ago | 1 answer | 0

Question

How can I get Matlab's Command Window to output the entire column vector of solutions?

Hi, Matlab's Command Window seems to cut off a long column vector of solutions. What is the default limit set to, and h...

3 months ago | 1 answer | 0

Question

How to store all of the converged roots found by Matlab's fsolve algorithm?

Hi, I'm practicing with Matlab's fsolve function, and am calling it with a few nested for loops that provide fsolve with var...

4 months ago | 1 answer | 0

Question

What is it called when I specify a vector output of solutions from, say, fsolve?

Hi, I have a simple question -- just a matter of lingo, I think: The fsolve algorithm gives all these outputs when it arr...

4 months ago | 1 answer | 0

Question

How can I improve this really slow code, which consists of several nested for loops?

Hi, So I've written these nested for loops, but it takes a very long time to execute this code: for T = linspace( 1, 5, 1...

4 months ago | 1 answer | 0

Question

In nested for-loops, how and where should I set the counting index (indices?) correctly, for doing numerical root-finding using fsolve?

Hi, Let's say I have a function, f, that maps R^3 to R^3, and I want to find its multivariable roots numerically, using fsol...

4 months ago | 1 answer | 0

Question

What information is conveyed by the different colors in Matlab's contourf( ) data plots?

Hi, Matlab has a contourf( ) function, which I used a little bit last night to plot the level sets of say, Z = f(x,y) = ...

4 months ago | 1 answer | 0

Question

Inner matrix dimensions must agree error message,

Hi, I'm getting an error message that says inner matrix dimensions must agree, but I checked both matrices and they seem fin...

4 months ago | 1 answer | 0

Question

Do vector fields mapping R^2 to R^2 have to be coded in separate function files, or can I define anonymous functions for them directly in the script file?

Hi, I've been writing functions from R^2 to R^2, i.e. F( f_1(x,y), f_2(x,y) )= (z_1, z_2), in separate function files, and th...

4 months ago | 1 answer | 0

Question

What is considered good practice for coding up a function's derivatives, e.g. its Jacobian and Hessian matrices?

Hi, I'm currently practicing numerical root-finding, using simple sets of nonlinear equations and writing my own solvers -- ...

4 months ago | 1 answer | 0

Question

Debugging Newton's Method code in two variables,

Hi, I wrote a simple code for Newton's Method in two variables but am having some trouble debugging it. Here's the message ...

4 months ago | 1 answer | 0

Question

How to get Matlab to return answers with ten-digit accuracy?

Hi, Answers returned by Matlab (e.g. from the ode45 solver, or from the wrapTo2Pi function that maps accumulating angles to [0,...

4 months ago | 2 answers | 0

Question

fsolve handling a composition of functions gives the error, "not enough input arguments"

I'm having some trouble using fsolve on a composition of functions. I've tried fsolve on a much simpler composition, and it wor...

4 months ago | 2 answers | 0

Question

How can I create elliptical-shaped markers?

I have two columns of data [X Y] that I would like to plot with elliptical-shaped markers.

3 years ago | 1 answer | 0

Question

How accurate is the numerical integrator, cumtrapz?

How accurate is the numerical integrator, cumtrapz?

3 years ago | 1 answer | 0

Question

how can I rotate the ellipses based on the orientation angle of (x_i,y_i)?

I would like to rotate the ellipses to show the orientation, theta, of the centered data points.

3 years ago | 2 answers | 0

Question

how can I center my data

I would like to draw an ellipse, and then center my data points on these ellipses.

3 years ago | 1 answer | 0

Question

"Inputs must be floats, namely single or double"

system of equations is: F = @(t, r, y) [y(1), y(2), y(3), f_integral] And then calling the ode solver: [t, y] = ode45(F...

3 years ago | 1 answer | 0