ex07_missing_values
This example demonstrates missing-value handling for two-dimensional NetCDF
grids. The primary has value 8 and stores a vertical missing band as NaN.
The secondary has value 2 and stores a horizontal missing band as -99999
without declaring that sentinel in its metadata.
The mergefile is:
primary secondary - cosine/cosine 0.25
secondary - - - -
The command supplies the secondary sentinel through GMT’s common input option:
gmt merge2d missing.merge2d -R0/100/0/100 -I1 -di-99999 -W -Gmerged.nc
The same merge can bridge enclosed gaps with linear Delaunay interpolation:
gmt merge2d missing.merge2d -R0/100/0/100 -I1 -di-99999 -Hl -W -Gmerged_filled.nc
Where both inputs are available, merge2d uses their weighted combination.
Where only one input is available, that value is retained regardless of the
merging weight. Where both are missing, the output is NaN. The output uses
NaN consistently even though the inputs use different representations.
With -Hl, each internal input gap is filled before resampling and merging;
original values are retained and gaps connected to an input-grid edge remain
missing.
Run:
./ex07_missing_values.sh
The script checks all three missing-data cases, verifies that the filled merge
has no remaining gaps, reconstructs the unfilled output at every available
node, and creates ex07_missing_values.png and ex07_missing_values.pdf.
Figures
