You have noisy data vectors x and y. You want to fit a cubic polynomial and then predict the value at x = 7. Which sequence of MATLAB commands correctly does this?

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MATLAB - Numerical Methods

You have noisy data vectors x and y. You want to fit a cubic polynomial and then predict the value at x = 7. Which sequence of MATLAB commands correctly does this?

Ap = polyfit(x, y, 3); y_pred = p(7);

Bf = fit(x, y, 'poly2'); y_pred = feval(f, 7);

Cp = polyfit(y, x, 3); y_pred = polyval(p, 7);

Df = fit(x, y, 'poly3'); y_pred = feval(f, 7);

Step-by-Step Solution

Solution:

Step 1: Choose correct fit function and degree
Using fit with 'poly3' fits a cubic polynomial to x and y.
Step 2: Predict value at x=7 using fit object
Use feval(f, 7) or f(7) to get predicted y value from the fit object.
Final Answer:
f = fit(x, y, 'poly3'); y_pred = feval(f, 7); -> Option D
Quick Check:
fit with 'poly3' and feval predicts y at 7 [OK]

Quick Trick: Use fit with 'poly3' and feval to predict [OK]

Common Mistakes:

Swapping x and y in polyfit
Using wrong polynomial degree
Using poly2 instead of poly3 for cubic fit

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You have noisy data vectors x and y. You want to fit a cubic polynomial and then predict the value at x = 7. Which sequence of MATLAB commands correctly does this?

Step 1: Choose correct fit function and degree

Step 2: Predict value at x=7 using fit object

Final Answer:

Quick Check:

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