Example 6: Plot vector map (e.g. wind, current)
===============================================

This example demonstrates how to import file and draw a section plot a wind map with GINCCO_lib
using :func:`GINCCO_lib.map_plot.map_draw_uv`.


Code Example
------------

Now we will import the library and the grid

.. code-block:: python

    # =========================
    # IMPORTS
    # =========================
    import numpy as np
    import GINCCO_lib as gc
    from netCDF4 import Dataset
    from datetime import *

    # =========================
    # CONFIGURATION
    # =========================
    tstart = datetime(2010, 1, 1)
    tend   = datetime(2010, 1, 10)

    path = '/work/users/tungnd/GOT271/GOT_REF5/OFFLINE/'

    # =========================
    # LOAD GRID
    # =========================
    fgrid = Dataset(path + 'grid.nc', 'r')
    lat_t = fgrid.variables['latitude_t'][:]
    lon_t = fgrid.variables['longitude_t'][:]
    mask_t_var = fgrid.variables['mask_t']
    if mask_t_var.ndim == 3:
        mask_t = mask_t_var[0, :, :]
    elif mask_t_var.ndim == 2:
        mask_t = mask_t_var[:, :]
    sin_t  = fgrid.variables['gridrotsin_t'][:,:]
    cos_t  = fgrid.variables['gridrotcos_t'][:,:]

Now import, interpolate and rotate data

.. code-block:: python

    # Step 1: Import data
    u_surface = gc.import_surface(path, 'u', tstart, tend, ignore_missing='False')
    v_surface = gc.import_surface(path, 'v', tstart, tend, ignore_missing='False')


    #Step 2: convert to t
    u_t, uncer_u = gc.interpolate_to_t(u_surface, stagger = 'u', mask_t = mask_t)
    v_t, uncer_v = gc.interpolate_to_t(v_surface, stagger = 'v', mask_t = mask_t)

    #Step 3: Choose a day and rotate it
    U1 =  u_t[1,:,:] * cos_t + v_t[1,:,:] * sin_t
    V1 = -u_t[1,:,:] * sin_t + v_t[1,:,:] * cos_t




Plot it

.. code-block:: python

    #Step 4: Draw
    gc.map_draw_uv(
        lon_min=105, lon_max=111,
        lat_min=16.5, lat_max=22,
        title="Surface current (example 6)",
        lon_data=lon_t,
        lat_data=lat_t,
        data_u= U1, data_v= V1,
        mask_ocean = mask_t,
        path_save="/prod/projects/data/tungnd/figure/",
        name_save="wind_map_example6",
        quiver_max_n=20,   # ~max arrows per axis (auto step so arrows <= quiver_max_n x quiver_max_n)
        quiver_scale=2  # higher is shorter arrow. lower is longer arrow



.. image:: ../_static/example6.png
   :width: 500px
   :align: center