traj: allow specifying the trajectory, observation and time dimensions/variables

tests/test_dims.py

@@ -12,3 +12,11 @@ def test_no_time_dim(barents):
     # can we use trajan without
 
     print(b.traj)
+
+def test_custom_dims(barents: xr.DataArray):
+    # b = barents.expand_dims('campaign')
+    b = barents.rename(trajectory='campaign')
+    print(b)
+
+    g = b.traj(trajectory_dim='campaign').gridtime('1H')
+    print(g)

trajan/traj.py

@@ -50,6 +50,39 @@ def __init__(self, ds, trajectory_dim, obs_dim, time_varname):
         self.obs_dim = obs_dim  # dimension along which time increases
         self.time_varname = time_varname
 
+    def __call__(self, trajectory_dim=None, obs_dim=None, time_varname=None):
+        """
+        Specify the trajectory, observation and time dimensions or variable names.
+
+
+        Parameters
+        ----------
+        trajectory_dim : string
+            Name of trajectory dimension (usually `trajectory` or `drifter`).
+
+        obs_dim : string
+            Name of observation dimension (usually `obs` or `time`).
+
+        time_varname : string
+            Name of time variable or dimension coordinate (usually `time`).
+
+
+        Returns
+        -------
+        traj : Traj
+            Traj accessor with manually specified coordinates and dimensions.
+        """
+        if trajectory_dim is not None:
+            self.trajectory_dim = trajectory_dim
+
+        if obs_dim is not None:
+            self.obs_dim = obs_dim
+
+        if time_varname is not None:
+            self.time_varname = time_varname
+
+        return self
+
     def __repr__(self):
         output = '=======================\n'
         output += 'TrajAn info:\n'