Quiver plot details and error

I've been handed a template code to make a quiver plot with little explanation, so I'm trying to learn more about quiver. First, it is giving me errors I don't know how to fix. Specifically, "input arguments must be numeric or objects which can be converted to double" starting with tmin. I was handed it the second way with function in it, but I get the same error (as well as syntax for the parentheses).

syms t y

f = @(t,y) t - y^2;

quiver(f, 0, 5, -3, 10, 'b')

syms t y

f = @(t,y) t-y.^2;

function quiver244(f, 0, 5;-3, 10, 'b')

For quiver plots in general: if I am asked to see how the graph changed when you start at different points, where can I input that? I am asked to prove my output using sampleplots, where I know I can put in a t0 and y0, but I have to do it with quiver first.

Any input would be appreciated.

Answer 1

[Ayush]

Hi Cassandra,

I understand that you are facing difficulty in working with the “quiver” function used for plotting in MATLAB.

Regarding the specific error you pointed out i.e. “input arguments must be numeric or objects which can be converted to double", this is caused by the symbolic variables:

sysm t y

This is incompatible with the “quiver” function. It only accepts numeric values or similar objects as mentioned in the error message as well. Refer to the below documentation to know more about the “quiver” function:

- Quiver or vector plot - MATLAB quiver - MathWorks India

Your second question can be catered by changing the initial conditions (“t0” and “y0”) in the definition of your function “f(t,y)”, in order to visualise the change from different starting points. Furthering this purpose, you can also consider different methods of plotting which are more suited for solution trajectories. Refer to the below documentation to know more about the plotting method in MATLAB:

-Types of MATLAB Plots - MATLAB & Simulink - MathWorks India

Hope it helps,

Regards,

Ayush Misra