How to plot polynomial function correctly?

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Fozle Rabbi
Fozle Rabbi 2022-8-31
评论： Walter Roberson 2022-9-1
From the given cooeficient polynomial functions how to draw an graph in matlab
P(x) = a_0+a_1x+a_2x^2. Whose graph passes through the points (1, 4), (4,73) and (5, 18). Also plot the function using MATLAB command (having proper title, x and y axis notation).
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Steven Lord
Steven Lord 2022-8-31
This sounds like a homework assignment. If it is, show us the code you've written to try to solve the problem and ask a specific question about where you're having difficulty and we may be able to provide some guidance.
If you aren't sure where to start because you're not familiar with how to write MATLAB code, I suggest you start with the free MATLAB Onramp tutorial to quickly learn the essentials of MATLAB.
If you aren't sure where to start because you're not familiar with the mathematics you'll need to solve the problem, I recommend asking your professor and/or teaching assistant for help.

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采纳的回答

Walter Roberson
Walter Roberson 2022-8-31
polyfit() and polyval() and plot()
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显示 5更早的评论
Walter Roberson
Walter Roberson 2022-9-1
You need to choose the x values to plot over.
You will use the given points to figure out what the coefficients are for the polynomial.Then, y will be the polynomial evaluated at your chosen x locations.
Walter Roberson
Walter Roberson 2022-9-1
Ran in:
syms x [3 1]
syms y [3 1]
vand = [ones(3,1), x, x.^2];
a0123 = simplify(vand \ y, 'steps', 20)
a0123 = 
sample_x = sort(randperm(10,3).');
sample_y = randi(100, 3, 1);
[sample_x, sample_y]
ans = 3×2
1 92 4 60 6 57
A0123 = simplify(subs(a0123, [x; y], [sample_x;sample_y]), 'steps', 20)
A0123 = 
X = -1:11;
Y = polyval(double(fliplr(A0123.')), X)
Y = 1×13
131.6667 110.0000 92.0000 77.6667 67.0000 60.0000 56.6667 57.0000 61.0000 68.6667 80.0000 95.0000 113.6667
plot(X, Y); hold on
scatter(sample_x, sample_y, 'r*'); hold off

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