Typically, data that's input to scikit-learn will be in the form of a NumPy array.

University of Michigan - Ann Arbor

NumPy is a Python library for scientific computing that contains support for some fundamental data structures used by scikit-learn, such as multi-dimensional arrays. Example import: `import numpy as np`

NumPy

Scikit-learn is an open-source machine learning library for programming languages. It provides support for  Support vector machine, random forest, gradient boosting, K-means and DBSCAN and classifications, regression and clustering algorithms, and design interoperable with numerical and scientific libraries(Numpy and Scipy). Like this, because Scikit-learn uses the scikit stack outside of the library, the biggest advantage is its compatibility with other libraries. Since the library has a unified interface, it is very simple to apply different methods.

Scikit-learn

NumPy Documentation

NumPy vs. Scikit-learn

What does the following code do?

Recall that "np.dot(a,b)" performs a matrix multiplication on a and b, whereas "a*b" performs an element-wise multiplication. Consider the two following random arrays "a" and "b": what is the shape of c?

Consider the following code: what will be c?

Consider the two following random arrays "a" and "b" below: what will be the shape of "c"?

Because the Numpy array is densely packed in memory due to its homogeneous type, Numpy gets around 30 times faster than Python.

Make big difference when handling big data.

Numpy Speed


In NumPy, there are two objects that are crucial to understanding how this library works. Those are:

1. N-dimensional array object (ndarray)

2. Universal function object (ufunc)

However, keep in mind that there are other objects that are built upon these that can be incorporated into whatever you're doing.

Fundamental Objects in NumPy

In python, there  is already data types that it has by default such as boolean, float, integer, etc. However, NumPy offers additional data types:

- i - integer
- b - boolean
- u - unsigned integer
- f - float
- c - complex float
- m - time delta
- M - date time
- O - object
- S - string
- U - unicode String
- V - fixed chunk of memory for other type (void)

Data Types in NumPy

Within the NumPy library, there are several types of mathematical functions built-in. These functions are typically used across elements of a NumPy array.

Types of Mathematical Functions:
- Trigonometric
- Rounding
- Exponents and Logarithms
- Arithmetic
- Other Special Functions

Mathematical Functions in NumPy

https://scikit-learn.org/stable/modules/generated/sklearn.neighbors.KNeighborsClassifier.html

Documentation for sklearn.neighbors.KNeighborsClassifier

Scikit-learn Cheat sheet

https://scikit-learn.org/stable/user_guide.html

Scikit-learn Documentation

Some helpful sklearn functions include:

- KNeighborsClassifier

- DummyClassifier

- DummyRegressor

- LabelEncoder

- OneHotEncoder

- Train Test Split Function

- make_regression

- make_friedman1

- make_classification

- SVC

- DecisionTreeClassifier

- RandomForestClassifier

- RandomForestRegressor

- GridSearchCV


Helpful Scikit-Learn functions

Whether on Mac or Windows, go to the command line and type:
```terminal
pip install -U scikit-learn
```

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