How to extend an array with linear interpolation

Question

What I want is to extend an array of length m to an array of length n (n>m), and interpolate the missing values linearly.

For example, I want to extend this array [1,5,1,7] to an array of length 7, the result should be [1,3,5,3,1,5,7], where the bold figures result from linear interpolation.

Is there an easy way to do this in Python? Thanks in advance.

What do you want to get if you extend the array [1, 5, 1, 7] to an array of length 6? — Aleksandr Kovalev
You can write a simple logic for what you want rather than finding an "easy way". — Pranav Totla
Then it should be, [1, 1+(5-1) * 3/5, 5+(1-5) * 1/5, 5+(1-5) * 4/5, 1+(7-1) * 2/5, 7] — Maytree23
@Maytree23 If you know what you want to get why don't you just write the code? — Aleksandr Kovalev
@Pranav Maytree23 might just be looking for a Pythonic way to it. — fixxxer

cfh cfh · Accepted Answer · 2015-05-04T06:28:46

The interp function from numpy can do what you want.

Example:

>>> xp = [1, 2, 3]
>>> fp = [3, 2, 0]
>>> np.interp(2.5, xp, fp)
1.0
>>> np.interp([0, 1, 1.5, 2.72, 3.14], xp, fp)
array([ 3. ,  3. ,  2.5 ,  0.56,  0. ])

How to extend an array with linear interpolation

1 Answers