Fit a curve so that a part of it is the same as another curve

I have a 1d array 'a' and a 1d array 'b'.

'a' is a length m and 'b' is a length n, where m>n.

I want to transform the array 'a' such that

a(1:n)=b

but also such that

a(n+1:m)

is also transform, i.e. so that the transformation is performed to the full array 'a' in matlab.

Is this possible in Matlab?

[Guillaume]

It's really not clear what you want to go in a(n+1:m). Can you explain it better. An actual example would be help:

a = 1:10;      %example input
b = [2 4 6 8]; %example input

newa = [2 4 6 8 ? ? ? ? ? ?]  %please fill in the ?

[Unai De Francisco]

In the case

 a = 1:10;      %example input
b = [2 4 6 8]; %example input
newa = [2 4 6 8 ? ? ? ? ? ?]  %please fill

I would like it to be filled by

newa = [2 4 6 8 10 12 14 16 18 20]

Answer 1

[Star Strider]

I am not certain what you want to do. The two functions that are most likely to give you the desired resultl are linspace (link) and interp1 (link). You will probably need to use both of them together.

EDIT —

With the new information, use interp1:

a = 1:10;
b = [2 4 6 8];
newa = interp1((1:4), b, a, 'linear', 'extrap')

producing:

newa =
     2     4     6     8    10    12    14    16    18    20