Hello GMT family,

I want to use `gravfft`

to compute gravity field signals due to `Bathy.nc`

, a `grdcut`

of GEBCO_2022 (downloaded from https://www.gebco.net/data_and_products/gridded_bathymetry_data/). There are no outputted signals for the -F options, except for gravity anomaly. Can someone kindly help me out? Thanks very much.

I used the script below in MATLAB:

```
gmt('grdsample GEBCO_2022.nc -rp -I1m -R-160/-145/-45/-35 -GBathy.nc')
Geoid = gmt('gravfft Bathy.nc -T7000/2700/3300/1035 -Fg -Z9000 -E1'); % no signal (NaN)
North = gmt('gravfft Bathy.nc -T7000/2700/3300/1035 -Fn -Z9000 -E1'); % no signal (NaN)
East = gmt('gravfft Bathy.nc -T7000/2700/3300/1035 -Fe -Z9000 -E1'); % no signal (NaN)
Grav = gmt('gravfft Bathy.nc -T7000/2700/3300/1035 -Ff -Z9000 -E1');
VGG = gmt('gravfft Bathy.nc -T7000/2700/3300/1035 -Fv -Z9000 -E1'); % no signal (NaN)
figure
subplot(2,3,1); imagesc(Geoid.x, Geoid.y, flipud(Geoid.z)); colorbar;
subplot(2,3,2); imagesc(North.x, North.y, flipud(North.z)); colorbar;
subplot(2,3,3); imagesc(East.x, East.y, flipud(East.z)); colorbar;
subplot(2,3,4); imagesc(Grav.x, Grav.y, flipud(Grav.z)); colorbar;
subplot(2,3,5); imagesc(VGG.x, VGG.y, flipud(VGG.z)); colorbar;
```