Environmental Science for SageMath

(Original setup by Jiri Kuncar)

This package contains helpers to deal with physical variables and units in SageMatch.

Installation

git clone https://github.com/schymans/environmental-science-for-sagemath
cd environmental-science-for-sagemath
sage -pip install -e .

Usage

Creating variables

To create custom variables, first import Variable and register:

from essm.variables import Variable, register

To define units, you can either import these units from the library, e.g.

from essm.variables.units import joule, kelvin, meter

Then you can define a custom variable with its name, description, domain, latex_name, and unit, e.g.:

class chamber_volume(Variable):
    """Volume of chamber."""
    latex_name = 'V_c'
    domain = 'real'
    name = 'V_c'
    unit = meter^3
    default = 1

Now, chamber_volume is displayed as V_c and you can type Variable.__registry__['chamber_volume'].__doc__ to obtain the documentation string. Variable.__defaults__ returns a dictionary with all variables and their default values, Variable.__units__ returns their units, and Variable.short_unit(chamber_volume) can be used to obtain the units in short notation.

You can import pre-defined variables as e.g.:

from essm.variables.chamber.insulation import *
from essm.variables.chamber.mass import *
from essm.variables.leaf.water_vapour import *

Creating equations

To create custom equations, fproceed similarly to avove, i.e. first import Variable and register:

from essm.equations import Equation, register

Then define an equation, e.g.:

class eq_Qi(Equation):
    """Calculate heat conduction through insulation material (Q_i)
    as a function of temperature difference ($dT_i$), and material
    properties.
    """
    expr = Q_i == dT_i*lambda_i*A_i/L_i