on-the-fly data reducers

pyVlsv/reduction.py

@@ -1100,6 +1100,7 @@ def makelambda(index):
 v5reducers["vg_jacobian_b"] = DataReducerVariable(["vg_dbxvoldx","vg_dbxvoldy","vg_dbxvoldz","vg_dbyvoldx","vg_dbyvoldy","vg_dbyvoldz","vg_dbzvoldx","vg_dbzvoldy","vg_dbzvoldz"], TensorFromScalars, "T/m", 1, latex=r"$\vec{J}$",latexunits=r"$\mathrm{A}\,\mathrm{m}^{-2}$")
 v5reducers["vg_jacobian_bper"] = DataReducerVariable(["vg_dperbxvoldx","vg_dperbxvoldy","vg_dperbxvoldz","vg_dperbyvoldx","vg_dperbyvoldy","vg_dperbyvoldz","vg_dperbzvoldx","vg_dperbzvoldy","vg_dperbzvoldz"], TensorFromScalars, "T/m", 1, latex=r"$\vec{J}$",latexunits=r"$\mathrm{A}\,\mathrm{m}^{-2}$")
 v5reducers["vg_j"] = DataReducerVariable(["vg_jacobian_bper"], J, "A/m^2", 1, latex=r"$\vec{J}$",latexunits=r"$\mathrm{A}\,\mathrm{m}^{-2}$")
+v5reducers["vg_j_parallel"] = DataReducerVariable(["vg_j", "vg_b_vol"], ParallelVectorComponent, "A/m^2", 1, latex=r"$J_\parallel$",latexunits=r"$\mathrm{A}\,\mathrm{m}^{-2}$")
 
 
 #multipopv5reducers

pyVlsv/vlsvreader.py

@@ -1676,6 +1676,28 @@ def read_variable(self, name, cellids=-1,operator="pass"):
 
  .. seealso:: :func:`read` :func:`read_variable_info`
  '''
+
+ # Handle custom variable names
+ # ex. (x-component unit vector Bx/|B|): name = '{vg_b_vol.x} / {vg_b_vol.magnitude}'
+ if '{' in name:
+ name_split = re.split(r"(\{.*?\})", name)
+ var_dct = {}
+ var_count = 0
+ for i, n in enumerate(name_split):
+ if '{' in n:
+ varname_x = 'var_{}'.format(var_count)
+ var_op = n[1:-1].split('.')
+ if len(var_op) == 2:
+ op = var_op[1] # note: overrides operator keyword
+ else:
+ op = operator
+ # Recursion: Evaluate variables in '{}'
+ var_dct[varname_x] = self.read_variable(var_op[0], cellids = cellids, operator = op)
+ var_count += 1
+ name_split[i] = varname_x
+ expr = ''.join(name_split)
+ return eval(expr, None, var_dct)
+
  cellids = get_data(cellids)
 
  # Wrapper, check if requesting an fsgrid variable