MATLAB: How to format this dsolve argument

differential equationsdsolveMATLABode

I'm not too familiar with solving DE's in matlab, but I keep getting an error when trying to implement this solution. Is there a syntax mistake I'm missing?

syms x
ode = x * diff(y, x) == 50 * x * diff(y, x, 2) - 40.3 * x + 101;
x_dot = dsolve(ode)

Best Answer

syms y(x)
ode = x * diff(y, x) == 50 * x * diff(y, x, 2) - 40.3 * x + 101;
x_dot = dsolve(ode)

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MATLAB: How to fix too many output argument

Dear Ma.Cathyrine Ravina,

There are several ways of doing this:

Use a Live Script (with control slider bar)
Create a MATLAB function and pass in the parameters you want
Create a GUI (if using a newer version of MATLAB I would recommend app designer and package as an APP for others)
Use the Symbolic Toolbox in MATLAB to calculate this (symbolicaly)

Please note I am using the latest version of MATLAB R2018b.

Live Script

Live Script is a MATLAB File that ends in mlx, which is designed for explaining concepts.

mass = 10;
gravity =9.5;
drag_second = 20;
t = 0:.1:10;
rk = mass*gravity - (drag_second/mass) * t;
plot(rk,t)

Please note that you would add the slider after mass, gravity and drag_second.

MATLAB Function

This is what you started to do and gave an error. As you need to pass in the variable, a, b.

function rk= myfunction(a,b);
    t = 0:.01:10; % defining values of t, starting a 0 and going to 10, with 0.01 steps
    rk= a*b - (c/a)*t; 
end

Appdesigner

This is the new way MathWorks has of creating APPS, or User Interfaces.

Type appdesigner in MATLAB
Follow the tutorial
Drag 3 Edit Numeric Fields into your canvas (give them the right name, e.g. mass,gravity,drag_second)
Drag 1 Axes (for visualizition)
Drag 1 Push button and call it Run (this is optional but easiest to get you going)
Select Push button, right click it, Callback, Add PushButtonFcn Callback - this will execute your MATLAB Code when pushed.
Add the following code:

mass = app.MassEditField.Value;  %gets the numeric value from user interface
gravity = app.GravityEditField.Value;
drag_second = app.drag_secondEditField.Value;
t = 0:.01:10; % Calculate time vector same as before
rk = mass*gravity - (drag_second/mass) * t;
plot(app.UIAxes,rk); % updates the chart

If you are happy with your App, feel free to package it and share it with others.

Hope that this helps you get started.

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MATLAB: How to fix too many output argument

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