.. _example_49:

(49) Analysis of the Atlantic seafloor depth/age relationship
-------------------------------------------------------------

In this example we show an example of data analysis using grids
of seafloor depth and age for a region in the south Atlantic.
We use module :doc:`grdsample </grdsample>` to convert the age
grid to the same pixel registration used by the depth grid.
Dumping separate x,y,z triplets with :doc:`grd2xyz </grd2xyz>`
lets us paste the output back via :doc:`gmtconvert </gmtconvert>`
to make binary tables of age,depth,depth.  Here, depth is repeated in
order to use :doc:`blockmode </blockmode>` for modal depth estimation
and :doc:`xyz2grd </xyz2grd>` for mapping the data density.
We image the density of (age,depth) points, overlay the modal depths
and their robust uncertainty bars, and compute and plot two models
for the expected depths as a function of age (see legend).  Note we
place most of the legend twice to achieve the thin-on-thick pen
effect in the legend.

.. literalinclude:: /_verbatim/ex49.txt
   :language: bash

.. figure:: /_images/ex49.*
   :width: 500 px
   :align: center

   Seafloor depth vs. age in the south Atlantic.
