Feature/formula (#77)

* initial working implementation of mean function with tests

* implemented polynomial mean function

* added finite difference tests to mean function unit tests

* made finite difference spacing a fixture

* changed fixed mean to use a function rather than lambda for derivative

* implemented mean function (note only unit tests assume zero mean, will write new ones during refactor of interface)

* fixed bugs in mean function implementation

* implemented additional mean function capabilities and wrote tests

* added docstrings to base mean function class

* documented mean sum class

* documented mean product class

* documented mean composite class

* documented fixed mean class

* added documentation and a few other checks to the fixed mean function implementations

* added documentation for coefficient class

* added documentation for polynomial mean class

* added module docstring and test for indexing error in composite mean

* added documentation page for mean function

* implemented power mean function

* fixed bugs in mean power and wrote unit tests

* basic working formula parser on linear terms

* wrote tokenizer function

* modified tokenizer to correct exponentiation and wrote expression parser

* removed unneeded function

* appear to have working formula parser

* fixed issue with square bracket parsing

* added class method and moved some things around

* added some unit tests for formula parsing

* implemented tests for tokenizing, parsing, and evaluating functions

* full set of unit tests for formulas and additional method in mean function to create from a formula

* changed base name and created functional interface for formula plus string methods

* added docstrings and renamed some functions

* added documentation for formulas and modified the mean function page a bit

* added patsy to install for testing and updated python version to 3.7

* updated version number for merge into devel

.travis.yml

@@ -1,9 +1,9 @@
 language: python
 python:
-  - "3.6"
+  - "3.7"
 install:
   - pip install -r requirements.txt
-  - pip install pytest-cov codecov
+  - pip install pytest-cov codecov patsy
   - python setup.py install
 script:
   - pytest --cov=./

docs/MeanFunction.rst

@@ -5,9 +5,10 @@ The ``MeanFunction`` Module
 **********************************
 
 .. automodule:: mogp_emulator.MeanFunction
+    :members: MeanFunction
     :noindex:
 
-.. autoclass:: mogp_emulator.MeanFunction.MeanFunction
+.. autoclass:: mogp_emulator.MeanFunction.MeanBase
     :members:
 
 .. autoclass:: mogp_emulator.MeanFunction.MeanSum
@@ -16,6 +17,9 @@ The ``MeanFunction`` Module
 .. autoclass:: mogp_emulator.MeanFunction.MeanProduct
     :members:
 
+.. autoclass:: mogp_emulator.MeanFunction.MeanPower
+    :members:
+
 .. autoclass:: mogp_emulator.MeanFunction.MeanComposite
     :members:
 

docs/formula.rst

@@ -0,0 +1,9 @@
+.. _formula:
+
+**********************************
+The ``formula`` Module
+**********************************
+
+.. automodule:: mogp_emulator.formula
+    :members:
+    :noindex:

docs/index.rst

@@ -14,6 +14,7 @@ Welcome to Multi-Output GP Emulator's documentation!
    DimensionReduction
    MultiOutputGP
    MeanFunction
+   formula
    Kernel
    ExperimentalDesign
    SequentialDesign