critical points on matlab?

hi everyone, can someone explien how to get critical point for a list on matlab

this is my code and i want to get the critical point can someone help please

L = [0.5 0.7 0.8 1.3 1.5];
T = [1.433 1.667 1.784 2.280 2.450;
     1.419 1.679 1.795 2.288 2.458;
     1.405 1.691 1.806 2.297 2.466];
T_AVG= mean(T);

coefs = polyfit(L,T_AVG,2);
x2 = 0.5:1:1.5;
curve= polyval(coefs,x2);
plot(L,T_AVG,x2,curve)
xlabel('Lenght')
ylabel('Time_AVG')
title('Periodic time of a pendulum')

AVG = mean(T_AVG)
STD = std(T_AVG)
MAX = max(T_AVG)
MIN = min(T_AVG)
VAR = var(T_AVG)

this is my code and i want to get the critical point can someone help

[KALYAN ACHARJYA]

What does "critical points" mean here?

Answer 1

[Matt J]

r = roots(polyder(coefs));

criticalPts= = r(~imag(r))

Answer 2

[KSSV]

L = [0.5 0.7 0.8 1.3 1.5];
T = [1.433 1.667 1.784 2.280 2.450;
     1.419 1.679 1.795 2.288 2.458;
     1.405 1.691 1.806 2.297 2.466];
T_AVG= mean(T);

coefs = polyfit(L,T_AVG,2);
x2 = 0.5:1:1.5;
curve= polyval(coefs,x2);
plot(L,T_AVG,x2,curve)
xlabel('Lenght')
ylabel('Time_AVG')
title('Periodic time of a pendulum')

AVG = mean(T_AVG) ;
STD = std(T_AVG) ;
MAX = max(T_AVG) ;
MIN = min(T_AVG) ;
VAR = var(T_AVG) ;

yi = [AVG  MAX MIN ] ; 
xi = interp1(T_AVG,L,yi) ;

hold on
plot(xi,yi,'*r')

[mohammad alsadi]

so this is the critical points thank you so much