Am I correct in my approach regarding interpolation?

Dear all

I have the vector

 A={
    [   NaN]
    [   NaN]
    [1.0877]
    [1.0909]
    [   NaN]
    [   NaN]
    [   NaN]
    [   NaN]
    [   NaN]
    [   NaN]
    [   NaN]
    [   NaN]
    [   NaN]
    [   NaN]
    [   NaN]
    [   NaN]
    [   NaN]
    [   NaN]
};

and the date vector

 D={'10/2008'
    '11/2008'
    '12/2008'
    '1/2009'
    '2/2009'
    '3/2009'
    '4/2009'
    '5/2009'
    '6/2009'
    '7/2009'
    '8/2009'
    '9/2009'
    '10/2009'
    '11/2009'
    '12/2009'
    '1/2010'
    '2/2010'
    '3/2010'
    '4/2010'
    '5/2010'
    '6/2010'
    '7/2010'
    '8/2010'
    '9/2010'
    '10/2010'
    '11/2010'
    '12/2010'
    '1/2011'
    '2/2011'
    '3/2011'
    '4/2011'
    '5/2011'
    '6/2011'
    '7/2011'
    '8/2011'
    '9/2011'
};

and I am doing interpolation

 xi  = datenum(D, 'mm/yyyy');
   z = interp1(xi(1:2:end),cell2mat(A(:,1)),xi);

   Equivalently,
   idx = ~isnan(cell2mat(A(:,1)));
z= interp1(xi(idx),cell2mat(A(idx,1)),xi);

Could you please verify that I am correct in my approach ?

thanks

Answer 1

[Azzi Abdelmalek]

v=cell2mat(A)
xi  = datenum(D, 'mm/yyyy');
z = interp1(xi(3:4),v(3:4),xi,'spline');

[tzaloupas]

Hi Azzi. thanks What is the difference between your approach and mine?Is this linear interpolation?

[Satyam Gaba]

No it's not a linear function. Spline interpolation can be used for polynomial interpolation for low degree polynomials as well as higher degrees.