How do I plot a polynomial equation and set of x-y coordinates on the same graph?

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Deleted User 2024-5-10

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https://ww2.mathworks.cn/matlabcentral/answers/2117226-how-do-i-plot-a-polynomial-equation-and-set-of-x-y-coordinates-on-the-same-graph

编辑： John Kelly 2024-5-20

I am trying to plot a polynmial and some x-y coordinates on the same graph. I need the coordinates to be visible and the lines to be distingushable from one another (eg. different colors).

Here is the measured data.

coefficients = [0.6252 -0.4165 0.1311 -0.0163 0.0009,-0.0000]
x = [2 5 8 11 14 20];
y = [0.20 0.29 0.44 0.50 0.66 0.56];

采纳的回答

Sam Chak 2024-5-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2117226-how-do-i-plot-a-polynomial-equation-and-set-of-x-y-coordinates-on-the-same-graph#answer_1455361

编辑：Sam Chak 2024-5-10

在 MATLAB Online 中打开

Edit: Your original polynomial coefficients are truncated. So, the polynomial cannot produce an accurate result.

%% data

x = [2 5 8 11 14 20];

y = [0.20 0.29 0.44 0.50 0.66 0.56];

%% polynomial coefficients

coefficients = [0.6252 -0.4165 0.1311 -0.0163 0.0009 -0.0000];

p = fliplr(coefficients)

p = 1x6

0 0.0009 -0.0163 0.1311 -0.4165 0.6252

format long

p = polyfit(x, y, numel(x)-1)

p = 1x6

-0.000018175582990 0.000901920438957 -0.016287722908091 0.131052812071305 -0.416499314128809 0.625240054869418

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%% points generated by polynomial

xx = linspace(x(1), x(end), 181);

yy = polyval(p, xx);

%% plot results

plot(x, y, 'o', 'markersize', 10), hold on

plot(xx, yy), grid on, xlabel('x'), xlabel('y')

legend('data', 'polynomial', 'location', 'northwest')

Thank you for that! Sorry to bother you, but I have another question. I’m trying to plot another point on the polynomial. I know the x coordinate is 17.5, but I don’t know the y coordinate. Is there a way I could plot the x coordinate on the polynomial and use the information from the graph to figure out the y coordinate? This coordinate needs to be distinguished from the points (eg. different colour).