If you have array of numbers A[i] you may try to do the next thing:
1. Calculate the exponential of this array
B[i] = Exp(A[i]);
2. Then make the linear interpolation of array B
C[i+di] = Linear interpolation of B[i]
3. Then calculate the ln(C[i+di])
A[i+di] = ln(C[i+di]);
As I understand you will get the logarithmic interpolation of your array A[i]
Oleg Chutko
