fplot differentiated symbolic equation

Hello there!

I'm trying to use the fplot function to plot an equation that I defined previously. However I think because I used syms and the diff() function to create the variable I am trying to plot, it is messing up the fplot function. My output is one graph which I already got to plot and an orange error message saying: '''The following error was reported evaluating the function in FunctionLine update: sym output type is not supported. Set 'UniformOutput' to false.'''

Any ideas for how to solve this? All other threads talk about arrayfun or something unrelated, if not, no worries, but thanks!

[robert hyde]

Here is my code (the error is in plotting Vg):

Answer 1

[Star Strider]

I would calculate the derivative and create the anonymous function for ‘Vg’ with:

Vg = matlabFunction(diff(Mg,t), 'Vars',{t});

With that change, it runs without error, although the plot generates a long ‘Warning’ message.

[robert hyde]

this worked perfectly and fast, thanks! MVP isn't just a label

[Star Strider]

As always, my pleasure!

Thank you very much for your compliment!

Answer 2

[Karan Gill]

You made a simple mistake. You used anonymous functions instead of symbolic functions. Declare a symbolic function using

syms Va(t)
Va(t) = t^2;

and plot it with fplot

fplot(Va)

See the second example in fplot doc: https://www.mathworks.com/help/symbolic/fplot.html

See symbolic functions: https://www.mathworks.com/help/symbolic/create-symbolic-functions.html

Comment if you have issues. If it works, please accept this answer.

[robert hyde]

This also worked and is a lot simpler to read, so I will use this as I am marked on how my code looks rather than it's run time, thank you very much!

Answer 3

[Omer Ali]

Thanks for asking this Rob! :)