Adding normalizer transformation

src/data/transforms/mod.rs

@@ -10,12 +10,14 @@
 //! commonly used in machine learning.
 
 pub mod minmax;
+pub mod normalize;
 pub mod standardize;
 pub mod shuffle;
 
 use learning::error;
 
 pub use self::minmax::MinMaxScaler;
+pub use self::normalize::Normalizer;
 pub use self::shuffle::Shuffler;
 pub use self::standardize::Standardizer;
 
@@ -31,4 +33,4 @@ pub trait Transformer<T> {
 pub trait Invertible<T> : Transformer<T> {
     /// Maps the inputs using the inverse of the fitted transform.
     fn inv_transform(&self, inputs: T) -> Result<T, error::Error>;
-}
+}

src/data/transforms/normalize.rs

@@ -0,0 +1,182 @@
+//! The Normalizing Transformer
+//!
+//! This module contains the `Normalizer` transformer.
+//!
+//! The `Normalizer` transformer is used to transform input data
+//! so that the norm of each row is equal to 1. By default the
+//! `Normalizer` uses the `Euclidean` norm.
+//!
+//! If input data has a row with all 0, `Normalizer` keeps the row as it is.
+//!
+//! Because transformation is performed per row independently,
+//! inverse transformation is not supported.
+//!
+//! # Examples
+//!
+//! ```
+//! use rusty_machine::data::transforms::{Transformer, Normalizer};
+//! use rusty_machine::linalg::Matrix;
+//!
+//! // Constructs a new `Normalizer`
+//! let mut transformer = Normalizer::default();
+//!
+//! let inputs = Matrix::new(2, 2, vec![-1.0, 2.0, 1.5, 3.0]);
+//!
+//! // Transform the inputs
+//! let transformed = transformer.transform(inputs).unwrap();
+//! ```
+
+use learning::error::{Error, ErrorKind};
+use linalg::{Matrix, MatrixSlice, BaseMatrix, BaseMatrixMut};
+use rulinalg::norm::{MatrixNorm, Euclidean};
+
+use super::Transformer;
+
+use libnum::Float;
+
+use std::marker::PhantomData;
+
+/// The Normalizer
+///
+/// The Normalizer provides an implementation of `Transformer`
+/// which allows us to transform the all rows to have the same norm.
+///
+/// The default `Normalizer` will use the `Euclidean` norm.
+///
+/// See the module description for more information.
+#[derive(Debug)]
+pub struct Normalizer<T: Float, M>
+    where for<'a> M: MatrixNorm<T, MatrixSlice<'a, T>>
+{
+    norm: M,
+    _marker: PhantomData<T>
+}
+
+/// Create a `Normalizer` with a Euclidean norm.
+impl<T: Float> Default for Normalizer<T, Euclidean> {
+    fn default() -> Self {
+        Normalizer {
+            norm: Euclidean,
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<T: Float, M> Normalizer<T, M>
+    where for<'a> M: MatrixNorm<T, MatrixSlice<'a, T>>
+{
+    /// Constructs a new `Normalizer` with given norm.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use rusty_machine::data::transforms::Normalizer;
+    /// use rusty_machine::linalg::norm::Euclidean;
+    ///
+    /// // Constructs a new `Normalizer`
+    /// let _ = Normalizer::<f64, Euclidean>::new(Euclidean);
+    /// ```
+    pub fn new(norm: M) -> Self {
+        Normalizer {
+            norm: norm,
+            _marker: PhantomData
+        }
+    }
+}
+
+impl<T: Float, M> Transformer<Matrix<T>> for Normalizer<T, M>
+    where for<'a> M: MatrixNorm<T, MatrixSlice<'a, T>>
+{
+
+    fn fit(&mut self, _: &Matrix<T>) -> Result<(), Error> {
+        // no op, because it has no parameter to fit
+        Ok(())
+    }
+
+    fn transform(&mut self, mut inputs: Matrix<T>) -> Result<Matrix<T>, Error> {
+        let dists: Vec<T> = inputs.row_iter().map(|m| self.norm.norm(&*m)).collect();
+        for (mut row, &d) in inputs.row_iter_mut().zip(dists.iter()) {
+
+            if !d.is_finite() {
+                return Err(Error::new(ErrorKind::InvalidData,
+                                      "Some data point is non-finite."));
+            } else if d != T::zero() {
+                // no change if distance is 0
+                *row /= d;
+            }
+        }
+        Ok(inputs)
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use super::super::Transformer;
+    use linalg::Matrix;
+
+    use std::f64;
+
+    #[test]
+    fn nan_data_test() {
+        let inputs = Matrix::new(2, 2, vec![f64::NAN; 4]);
+        let mut normalizer = Normalizer::default();
+        let res = normalizer.transform(inputs);
+        assert!(res.is_err());
+    }
+
+    #[test]
+    fn inf_data_test() {
+        let inputs = Matrix::new(2, 2, vec![f64::INFINITY; 4]);
+        let mut normalizer = Normalizer::default();
+        let res = normalizer.transform(inputs);
+        assert!(res.is_err());
+    }
+
+    #[test]
+    fn single_row_test() {
+        let inputs = matrix![1.0, 2.0];
+        let mut normalizer = Normalizer::default();
+        let transformed = normalizer.transform(inputs).unwrap();
+
+        let exp = matrix![0.4472135954999579, 0.8944271909999159];
+        assert_matrix_eq!(transformed, exp);
+    }
+
+    #[test]
+    fn basic_normalizer_test() {
+        let inputs = matrix![-1.0f32, 2.0;
+                             0.0, 3.0];
+
+        let mut normalizer = Normalizer::default();
+        let transformed = normalizer.transform(inputs).unwrap();
+
+        let exp = matrix![-0.4472135954999579, 0.8944271909999159;
+                          0., 1.];
+        assert_matrix_eq!(transformed, exp);
+
+        let inputs = matrix![1., 2.;
+                             10., 20.;
+                             100., 200.];
+
+        let transformed = normalizer.transform(inputs).unwrap();
+
+        let exp = matrix![0.4472135954999579, 0.8944271909999159;
+                          0.4472135954999579, 0.8944271909999159;
+                          0.4472135954999579, 0.8944271909999159];
+        assert_matrix_eq!(transformed, exp);
+
+        let inputs = matrix![1., 2., 10.;
+                             0., 10., 20.;
+                             100., 10., 200.;
+                             0., 0., 0.];
+        let transformed = normalizer.transform(inputs).unwrap();
+
+        let exp = matrix![0.09759000729485333, 0.19518001458970666, 0.9759000729485332;
+                          0., 0.4472135954999579, 0.8944271909999159;
+                          0.4467670516087703, 0.04467670516087703, 0.8935341032175406;
+                          0., 0., 0.];
+        assert_matrix_eq!(transformed, exp);
+    }
+}