Interpolation (interp1) in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the interp1 function in MATLAB?

The interp1 function is used to find intermediate values between known data points in one dimension. It helps estimate values at points where data is not explicitly given.

beginner

What are the basic inputs required for interp1?

You need three inputs: <br>1. x: known data points on the x-axis, <br>2. v: known values at points x, <br>3. xq: query points where you want to estimate values.

beginner

Name two common interpolation methods used with interp1.

Two common methods are:<br>1. 'linear': connects points with straight lines.<br>2. 'nearest': uses the value of the closest known point.

intermediate

What happens if the query points xq are outside the range of known points x in interp1?

By default, interp1 returns NaN for query points outside the known range. You can change this behavior by specifying an extrapolation method.

beginner

How do you specify the interpolation method in interp1?

You add the method as the fourth argument, for example: interp1(x, v, xq, 'spline') uses spline interpolation.

What does interp1(x, v, xq, 'nearest') do?

A Connects points with straight lines to estimate values.

B Returns NaN for all query points.

C Uses polynomial fitting for interpolation.

D Returns the value of the closest known point to each query point.

The 'nearest' method picks the value of the closest known point to each query point.

If xq is outside the range of x, what is the default output of interp1?

A NaN (Not a Number).

B Extrapolated value based on nearest point.

C Zero.

D Error message.

By default, interp1 returns NaN for query points outside the known data range.

Which input to interp1 represents the known values at data points?

A <code>x</code>

B <code>xq</code>

C <code>v</code>

D <code>method</code>

v holds the known values corresponding to points x.

What interpolation method connects points with straight lines?

A 'nearest'

B 'linear'

C 'pchip'

D 'spline'

The 'linear' method connects known points with straight lines.

How do you ask interp1 to use spline interpolation?

A interp1(x, v, xq, 'spline')

B interp1(x, v, xq, 'nearest')

C interp1(x, v, xq, 'linear')

D interp1(x, v, xq)

Passing 'spline' as the method argument uses spline interpolation.

Explain how interp1 works and when you would use it.

Think about filling gaps between known points.

Describe the difference between 'nearest' and 'linear' interpolation methods in interp1.

Consider how the estimated values change between points.