add installation and example to readme file

README.rst

@@ -8,3 +8,63 @@ XSpline
 =======
 
 Advanced spline package that provides b-spline bases, their derivatives and integrals.
+
+
+Installation
+------------
+
+XSpline can be install via
+
+.. code-block:: bash
+
+    pip install xspline>=0.1.0
+
+
+Requirements
+------------
+
+XSpline requires python 3.10 or higher. XSpline only depends on ``numpy>=1.25.1``.
+
+
+Usage
+-----
+
+There are two main use-cases.
+
+.. code-block:: python
+    
+    import numpy as np
+    import matplotlib.pyplot as plt
+    from xspline import XSpline
+
+    spline = XSpline(knots=[0, 0.25, 0.5, 0.75, 1], degree=3)
+    x = np.arange(0, 1.01, 0.01)
+
+
+one is to use XSpline as a univariate function. In this case, user must provide
+coefficients for the spline bases.
+
+.. code-block:: python
+
+    np.random.seed(123)
+    spline.coef = np.random.randn(len(spline))
+    y = spline(x)
+
+    fig, ax = plt.subplots(figsize=(8, 3))
+    ax.plot(x, y)
+    ax.set_title("Usecase 1", loc="left")
+
+.. image:: images/readme_usage_0.png
+    :alt: usecase_1
+
+The other is to obtain the design matrix for other modeling uses.
+
+.. code-block:: python
+
+    design_mat = spline.get_design_mat(x)
+
+    fig, ax = plt.subplots(figsize=(8, 3))
+    ax.plot(x, design_mat)
+
+.. image:: images/readme_usage_1.png
+    :alt: usecase_2

pyproject.toml

@@ -4,15 +4,15 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "xspline"
-version = "1.0.0"
+version = "0.1.0"
 description = "Advanced spline package that provides b-spline bases, their derivatives and integrals"
 readme = "REDME.rst"
 requires-python = ">=3.10"
 license = { file = "LICENSE" }
 authors = [
     { name = "IHME Math Sciences", email = "ihme.math.sciences@gmail.com" },
 ]
-dependencies = ["numpy"]
+dependencies = ["numpy>=1.25.1"]
 
 [project.optional-dependencies]
 test = ["pytest"]
@@ -25,4 +25,4 @@ github = "https://github.com/zhengp0/xspline"
 project = "xspline"
 author = "IHME Math Sciences"
 copyright = "2023, IHME Math Sciences"
-version = "1.0.0"
+version = "0.1.0"