# Spines¶

**Backbones for parameterized models.**

## About¶

Spines was built to provide a skeleton for Model classes: a common interface for users to build models around (with some tools and utilities which take advantage of those commonalities). It’s core Model class is similar, in structure, to some of scikit-learn’s underlying Estimator classes - but with a single set of unified functions for all models, namely:

Build

Fit

Predict

Score

Error

The predict method is the only one that’s required to be implemented, though the others are likely useful most of the time (and often required to take advantage of some of the additional utilities provided by spines).

Spines also incorporates automatic version management for your models - something akin to a very lightweight git - but for individual models. It also caches results generated during various iterations of the development/fitting process so that they’re not lost during - something that can (and often does) happen during very iterative model development work.

## Simple Example¶

To demonstrate how to build a model with spines we’ll use a toy example of a simple linear regression model. First we import what we’ll need:

```
import numpy as np
from spines import Model, Parameter
```

Now we’ll create the model class:

```
class LinearRegression(Model):
"""
Simple linear regression model
y = mx + b
"""
m = Parameter(float)
b = Parameter(float)
def fit(self, x, y):
covs = np.cov(x, y)
self.m = (covs[0, 1] / np.var(x))
self.b = np.mean(y) - (self.m * np.mean(x))
def predict(self, x):
return (self.m * x) + self.b
```

Now that we have the model we can generate some random data to fit it with:

```
x = np.random.rand(10)
y = 3.0 * x
x += np.random.normal(scale=0.05, size=(10,))
```

Then create and fit the model:

```
model = LinearRegression()
model.fit(x, y)
```

If we look at the `model.parameters`

attribute we should see something
like `b`

being a small-ish number around 0 and `m`

being close to
3.

See the quick start page for a slightly more in-depth example.