EquatIC v1.0.4

Equatic is a string equation parser which utilises the Sympy and Numpy libraries to evaluate equations for a given set of values, the two aims being to include more functions than those included in other methods and to evaluate values without the risk of 'danger' which is currently present within these.

Installation

There are two methods for installing EquatIC at present. You can either use pip from the package folder:

pip install -r requirements.txt

or you can run the setup script:

python setup.py

to ensure EquatIC is behaving as expected you may also wish to run the included tests:

python setup.py test

both methods install EquatIC as well as the other python packages it requires to run.

Quick Use

You can quickly parse either a single value or range of values using the following syntax:

equatic.parse('npdf(x)', 0.5)

In the case of using a value range either a length 2 or length 3 list can be given where the third argument is the optional number of points to calculate.

equatic.parse('npdf(x)', [-0.5, 0.5])

or

equatic.parse('npdf(x)', func_range=[-0.5, 0.5, 100], debug='ERROR')

Creating a Parser

Below is an example of how the parser can be used, here a set of x values is generated using Numpy and then handed to the parser with the function then being parsed after. The x value set is not compulsary however when a set is specified the parse_equation_string method will return the resultant values for f(x).

from equatic import EquationParser      
import numpy as np


# Create a set of x values between -5pi and 5pi

x = np.linspace(-5*np.pi, 5*np.pi, 1000)

# Create a parser object giving the generated x values

parser = EquationParser( 'my parser'           ,
                          xarray     =  x      , 
                          log        =  'ERROR'
                       )

# Finally tell the parser the equation to process

y = parser.parse_equation_string('sinc(x)')


# Use MatplotLib to plot the results!

import matplotlib.pyplot as plt
plt.plot(x, y)
plt.show()

Evaluating the Equation for a Single Value

Once the parser has been given an equation to process it can then evaluated it for a single value/list of values outside of initialisation.

parser.calculate(0.5) parser.calculate([0.5, 0.6, 0.7])

Specifying Logging Detail

By default EquatIC parsers are set to be run with the logging level set to 'INFO'. This can be specified either when initialising the parser itself or after using the function:

parser.set_logger_level('DEBUG')

for a full list of options see the documentation for the logging python module.

EquatIC Console App

Currently in early development but available in this version is the console application which can currently be found in the equatic directory as equatic_app.py within the main package folder. The command to run the application can itself take options:

• --verbose or -v sets the logging option to DEBUG
• --info or -i sets the logging option to INFO
• --save or -s saves the output within the session
• --saveas or -o does the same as the above but allows the user to specify an output file name

python equatic_app.py --verbose --saveas 'my_session.log'

EquatIC[0]: tan(1)
1.55740772465
EquatIC[1]: cos(1)
0.540302305868

the session is exited using quit or q.

Plotting Functions

EquatIC includes a function for plotting via MatplotLib:

equatic.plot(equation_string, func_range=[0.1, 10], xlabel='x', ylabel='y', debug='ERROR', plot_opts = '-', save=None, show=True, title=None)

For example if we wanted to plot the function tan(x-1) in the range [0,3.14] we would do the following:

equatic.plot(   'tan(x-1)'                                      , 
                [0,3.14]                                        ,
                xlabel    = 'x'                                 ,
                ylabel    = 'f(x)'                              , 
                title     = r"Plot of the Function '$tan(x-1)$'",
                plot_opts = 'o'                                 , 
                save      = 'my_plot.png'                       )

Note EquatIC maintains MatplotLib's support of LaTeX strings for titles.

Add Your Own Functions

EquatIC parsers can be expanded to include additional single argument functions using the add_function method.

For example say we wanted to add a simple function quad which multiplies any number by 4, firstly we define our function:

def quad(x):
    return 4*x

then we add it to the parser's functions library:

parser.add_function('quad', quad)

we can now perform calculations using it:

parser.parse_equation_string('quad(x)')
parser.plot()

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