Question on Graphing / Plotting

Currently i have:

 syms x
Y = sqrt ((x^4 - x + 1) / x^4 + x +1 )

I take the derivative of that using diff Y and get one.

The problem I am having is trying to graph the original Y and the diff Y on the same screen. It wont allow me to plot either through the workspace and was wondering if theres a simple command to use to graph them for comparison. Any help would be appreciated thank you!

Answer 1

[Sean de Wolski]

You're likely looking for ezplot. Regular plot doesn't play well with syms:

syms x
Y = sin(x);
dY = diff(Y);
ezplot(Y,dY);

[Frank]

i tried ezplot(Y,dY) with Y = (x + (x^4 - x + 1)/x^4 + 1)^(1/2) dY = diff(Y)

When plotted all i get is one line so im not sure if thats right or not

[Walter Roberson]

There is only one variable in the equation; there is no reason to expect more than one line. The line is, though discontinuous at 0.

[Frank]

understood thank you for clarifying!

Answer 2

[Walter Roberson]

diff Y

means

diff('Y')

Since the only variable found in that is Y, that means

diff('Y', 'Y')

and the derivative of that is clearly 1.

Perhaps you meant

diff(Y)

[Frank]

diff(Y) gives me the right answer thank you but for some reason I cannot plot the ans and the original Y from the workspace. The Error I receive is:

The plot requires the following inputs:A matrix/vector, or 2 vectors/matrices of compatible size, with an optional linespec

[Walter Roberson]

f = matlabFunction(diff(Y), 'vars', x);
t = linspace(-3,3,100);
plot(t, f(t))