# 4th degree question ploting

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AHMED AKBAS on 26 Nov 2020
Commented: John D'Errico on 29 Nov 2020
Ctg =[0.322;0.122;0.084;0.053;0.031;0.01];
t =[0 20 40 60 80 100];
% 4th degree Equation
R = 1.914e-08*t4 -4.753e-06*t3 + 0.0004167*t2 – 0.01639*t+ 0.3213
How can I plot it to be like the attached image? please anyony

#### 1 Comment

John D'Errico on 26 Nov 2020
What have you tried? You should realize you will raise t to the 4th power as t.^4.

Image Analyst on 26 Nov 2020
Try this:
Ctg =[0.322; 0.122; 0.084; 0.053; 0.031; 0.01];
t =[0; 20; 40; 60; 80; 100];
plot(t, Ctg, 'ko', 'LineWidth', 2, 'MarkerSize', 15);
hold on;
% Estimate the coefficients for a 4th order polynomial.
coefficients = polyfit(t, Ctg, 4)
% Make a new x
t = linspace(min(t), max(t), 1000);
% 4th degree Equation
R = coefficients(1)*t.^4 + coefficients(2)*t.^3 + coefficients(3)*t.^2 + coefficients(4)*t+ coefficients(5);
plot(t, R, 'b-', 'LineWidth', 2);
grid on;

AHMED AKBAS on 29 Nov 2020
Thanks a lot, this is what Im looking for

#### 1 Comment

John D'Errico on 29 Nov 2020

R2020a

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