how can we display our real roots or points
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adriana resendez
on 3 Mar 2015
Commented: Star Strider
on 3 Mar 2015
>> f = @(x) x^3-3*x-1;
>> fplot(f, [-10 10]); grid on;
2 Comments
Andrew Newell
on 3 Mar 2015
Do you want to find the roots or just change the display so you can see the crossings?
Accepted Answer
Star Strider
on 3 Mar 2015
Edited: Star Strider
on 3 Mar 2015
Use the roots function:
xr = roots([1 0 -3 -1]);
They all happen to be real. This gives the x-values, so if you want to plot them, the y vector is:
yr = zeros(size(xr));
4 Comments
Star Strider
on 3 Mar 2015
I changed ‘r’ to ‘xr’ when I created ‘yr’ and forgot to change it in ‘yr’. The code is consistent now.
With a couple tweaks, you can plot everything easily:
f = @(x) x^3-3*x-1;
xr = roots([1 0 -3 -1]);
yr = zeros(size(xr));
figure(1)
fplot(f, [-10 10], '-r')
hold on
plot(xr, yr, 'bp')
hold off
grid on
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