graph the function using ezplot() and plot()

clc
clear all
syms x
 
ezplot(@(x) -3*x^3+5*x ,[-2.5, 2.5])
plot()

I have a function 2y^2 = -3x^3+5x , -2.5≤x≤2.5.

I used ezplot, but it is not able to read the y function. How can I make a graph of the function using ezplot and plot?

[Dr. Elangovan]

I don't know

Answer 1

[Geoff Hayes]

Jay - are you observing an error? If so, what is it?

Or do not use the syms x and just call

ezplot(@(x) -3*x^3+5*x ,[-2.5, 2.5])

You may see some warnings such as

Warning: Function failed to evaluate on array inputs; vectorizing the function may speed up
its evaluation and avoid the need to loop over array elements. 

and so you can just do the following instead

ezplot(@(x) -3*x.^3+5*x ,[-2.5, 2.5])

where the anonymous function has been vectorized.

[madhan ravi]

Agree with Geoff Hayes:

ezplot(@(x,y) -3*x.^3+5*x-2*y.^2) % adjust your limit for the two variables , see the doc for two variable limits

Answer 2

[Star Strider]

Perhaps this —

syms x y 
% 2y^2 = -3x^3+5x , -2.5≤x≤2.5.
Eqn = 2*y^2 == -3*x^3+5*x                                   % Add Operators

Eqn = 

Eqn = isolate(Eqn, y)

Eqn = 

y = rhs(Eqn)

y = 

xterm = solve(sqrt(-x)*sqrt(3*x^2-5))

xterm = 

infvals = double(xterm)

infvals = 3×1

0 -1.2910 1.2910

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figure
fplot(y, [-2.5 2.5])
grid
xlabel('X')
ylabel('Y')
title("$"+string(latex(Eqn)+"$"), Interpreter='LaTeX', FontSize=16)

yfcn = matlabFunction(y)

yfcn = function_handle with value:
    @(x)(sqrt(2.0).*sqrt(-x).*sqrt(x.^2.*3.0-5.0))./2.0

xv = linspace(-2.5, 2.5, 250);

figure
plot(xv, abs(yfcn(xv)), DisplayName='|y(x)|')
hold on
plot(xv, real(yfcn(xv)), DisplayName='Re(y(x))')
plot(xv, imag(yfcn(xv)), DisplayName='Im(y(x))')
hold off
grid
xlabel('X')
ylabel('Y')
title("$"+string(latex(Eqn)+"$"), Interpreter='LaTeX', FontSize=16)
legend(Location='best')
xline(infvals, '--k', DisplayName='Discontinuity')

The isolate function was introduced in R2017a.

.