Curve fitting (polyfit, fit) in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to fit a polynomial of degree 2 to data points.

MATLAB

p = polyfit(x, y, [1]);

Drag options to blanks, or click blank then click option'

A1

B2

C0

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using degree 1 fits a straight line, not a curve.

Using degree 0 fits a constant, which is not a curve.

The third argument to polyfit specifies the degree of the polynomial. Here, degree 2 fits a quadratic curve.

2fill in blank

medium

Complete the code to evaluate the polynomial fit at points x_new.

MATLAB

y_fit = polyval(p, [1]);

Drag options to blanks, or click blank then click option'

Ax_new

By_new

Cp

Dx

Attempts:

3 left

💡 Hint

Common Mistakes

Using y-values instead of x-values as input to polyval.

Passing the coefficients vector again instead of points.

polyval evaluates the polynomial coefficients p at the points given by x_new.

3fill in blank

hard

Fix the error in the code to create a fit object for a linear fit.

MATLAB

f = fit(x, y, [1]);

Drag options to blanks, or click blank then click option'

A'poly2'

B'linear'

C'exp1'

D'poly1'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'linear' which is not a valid model name for fit.

Using 'poly2' which fits a quadratic, not linear.

To fit a linear polynomial using fit, use the model name 'poly1'.

4fill in blank

hard

Fill both blanks to create a quadratic fit and plot it.

MATLAB

f = fit(x, y, [1]);
plot(f, [2]);

Drag options to blanks, or click blank then click option'

A'poly2'

Bx

Cx_new

D'poly1'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'poly1' instead of 'poly2' for quadratic fit.

Plotting against original x instead of new x-values.

'poly2' fits a quadratic polynomial. To plot the fit against new x-values, use x_new.

5fill in blank

hard

Fill all three blanks to create a cubic polynomial fit, evaluate it, and plot the results.

MATLAB

p = polyfit(x, y, [1]);
y_fit = polyval(p, [2]);
plot([3], y_fit, '-r');

Drag options to blanks, or click blank then click option'

A3

Bx_new

Dx

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong degree for cubic fit.

Plotting against original x instead of new x-values.

Degree 3 fits a cubic polynomial. Evaluate at x_new and plot y_fit against x_new.