# MATLAB doesn't plot my function

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Pedro Almeida il 6 Dic 2022
Commentato: Askic V il 6 Dic 2022
This is probably a dumb question but when I try to plot this function nothing appears:
format long
y = @(x) - sin(x);
z = @(x) x.^2;
test1 = @(x) y(x)-z(x);
x = fzero(test1,[0 1])
plot(test1)
It also gives my the following error:
error: unary operator '.'' not implemented for 'function handle' operands
error: called from
__plt__>__plt1__ at line 189 column 8
__plt__ at line 118 column 18
plot at line 229 column 10
ex1 at line 6 column 1
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### Risposta accettata

Alan Stevens il 6 Dic 2022
Try
fplot(test1)
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Pedro Almeida il 6 Dic 2022
I'm sorry, but what does this line do exactly? I'm new to MATLAB so appologies if this is too simple.
f_val = feval(test1, t);
Askic V il 6 Dic 2022
It evaluates the function test1. Please have a look at the documentation:
https://www.mathworks.com/help/matlab/ref/feval.html

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### Più risposte (1)

Sam Chak il 6 Dic 2022
You probably want to plot like this?
y = @(x) - sin(x);
z = @(x) x.^2;
fun = @(x) y(x) - z(x);
fplot(y, [-pi pi]), hold on
fplot(z, [-pi pi]),
xsol1 = fzero(fun, -1)
xsol1 = -0.8767
xsol2 = fzero(fun, 1)
xsol2 = 6.2882e-26
plot(xsol1, y(xsol1), 'o')
plot(xsol2, y(xsol2), 'p'), hold off
xlabel('x'), grid on,
legend('sin(x)', 'x^2')
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Askic V il 6 Dic 2022
Great example!

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