Document Actions
LANCZOS
Appendix A Sec27.
LANCZOS
LANCZOS(A, F1, F2, N ) Returns the argument, bandpass-filtered in time using a Lanczos filter.
|
Arguments: |
A |
Variable with a regular time axis; may be a function of x, y, and/or z |
|
F1 |
Low frequency cutoff |
|
|
F2 |
High frequency cutoff |
|
|
N |
Number of weights (must be odd) |
|
|
Result Axes: |
X |
Inherited from A |
|
Y |
Inherited from A |
|
|
Z |
Inherited from A |
|
|
T |
Inherited from A |
For details see: Duchon, C. E., 1979: Lanczos filtering in one and two dimensions. J. of App. Met., 18, 1016-1022. This function is based on code written by Bill Gustafson at UC Davis.
Example: apply filter to series after removing its mean.
yes? use monthly_navy_winds
yes? let aa = uwnd[i=50,j=20]
yes? let az = aa - aa[t=@ave]
yes? plot az
yes? plot/over lanczos(az, 0.05, 0.1, 11)
yes? plot/over lanczos(az, 0.1, 0.2, 11)