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Last seen: 3 days ago |  Active since 2017

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Deciding when to call a Matlab function: Within my symbolic math code, or within my converted numerical code?
Hi there! I wrote a symbolic math code and used the algebraic solver solve( ) to get the equations that I want. I then converte...

3 days ago | 1 answer | 0

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answer

Question


Writing ODE equations for ode45 to solve;
Hi there! I have a basic question to ask here, regarding writing the first-order equations for ode45 to solve. Let's say I am ...

22 days ago | 1 answer | 0

1

answer

Question


ode45 integration issues for some choices of physical parameters,
Hi there! I have a simple, two-dimensional, ode model that solves for the trajectory of a flat plate falling through a fluid fl...

1 month ago | 2 answers | 0

2

answers

Question


Simple question about creating an anonymous function,
Hi there! Using a Matlab function file, I wrote an ode model model(t, z, p), where p stores all of my physical parameters, suc...

1 month ago | 2 answers | 0

2

answers

Question


How to animate background flow field that an object is moving through?
Hi there! I now have a decent code that solves an ode model of mine, using ode45. It is about a rigid plate falling freely thro...

1 month ago | 1 answer | 0

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answer

Question


How can I run code just once, for multiple intervals of numbers?
Let's say I want to calculate things for alpha ranging from 0 to 2pi. I've written if / else-if statements to do this: alpha ...

2 months ago | 1 answer | 0

1

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Question


How to loop through values?
Let’s say I have 11 values of beta, evenly-spaced with linspace( ). And let’s say for each value of beta, I want to compute some...

2 months ago | 1 answer | 0

1

answer

Question


Only the first if-statement block executes,
Hi there! I wrote an if-statement, followed by an if-else statement, followed by another if-else statement, followed by the end...

2 months ago | 1 answer | 0

1

answer

Question


Using an anonymous function handle as input into another function handle
Hi there! I have a question that's mostly about syntax: Let's say I write the anonymous function handle (for a program to give ...

1 year ago | 3 answers | 0

3

answers

Question


Writing a system of ODEs for ode45
Hi, I wrote a .m-file that has three second-order differential equations, broken down into six first-order equations. When I r...

1 year ago | 1 answer | 0

1

answer

Question


How to put fsolve in a loop, using 2 unknowns?
Hi, I want to write a code that asks fsolve to go through some combinations of guesses and then find all the roots (xdot, yd...

3 years ago | 1 answer | 0

1

answer

Question


Filled figures, saved as eps or pdf, now have weird lines when zoomed in, while png files do not,
Hi, My filled figures, e.g. ellipses, using either the fill() or patch functions, and saved as eps or pdf files, now have weir...

3 years ago | 1 answer | 0

1

answer

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...

4 years ago | 0 answers | 0

0

answers

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...

4 years ago | 1 answer | 0

1

answer

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...

4 years ago | 1 answer | 0

1

answer

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 years ago | 1 answer | 0

1

answer

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 years ago | 1 answer | 0

1

answer

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 years ago | 1 answer | 0

1

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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 years ago | 1 answer | 0

1

answer

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 years ago | 1 answer | 0

1

answer

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 years ago | 1 answer | 0

1

answer

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 years ago | 1 answer | 0

1

answer

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 years ago | 1 answer | 0

1

answer

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 years ago | 1 answer | 0

1

answer

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 years ago | 2 answers | 0

2

answers

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 years ago | 2 answers | 0

2

answers

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.

7 years ago | 1 answer | 0

1

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Question


How accurate is the numerical integrator, cumtrapz?
How accurate is the numerical integrator, cumtrapz?

7 years ago | 1 answer | 0

1

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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.

7 years ago | 2 answers | 0

2

answers

Question


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

7 years ago | 1 answer | 0

1

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