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</pre><pre class="rust"><code><span class="doccomment">//! Support Vector Machine Module
//!
//! Contains implementation of Support Vector Machine using the
//! [Pegasos training algorithm](http://ttic.uchicago.edu/~nati/Publications/PegasosMPB.pdf).
//!
//! The SVM models currently only support binary classification.
//! The model inputs should be a matrix and the training targets are
//! in the form of a vector of `-1`s and `1`s.
//!
//! # Examples
//!
//! ```
//! use rusty_machine::learning::svm::SVM;
//! use rusty_machine::learning::SupModel;
//!
//! use rusty_machine::linalg::Matrix;
//! use rusty_machine::linalg::Vector;
//!
//! let inputs = Matrix::new(4,1,vec![1.0,3.0,5.0,7.0]);
//! let targets = Vector::new(vec![-1.,-1.,1.,1.]);
//!
//! let mut svm_mod = SVM::default();
//!
//! // Train the model
//! svm_mod.train(&amp;inputs, &amp;targets).unwrap();
//!
//! // Now we&#39;ll predict a new point
//! let new_point = Matrix::new(1,1,vec![10.]);
//! let output = svm_mod.predict(&amp;new_point).unwrap();
//!
//! // Hopefully we classified our new point correctly!
//! assert!(output[0] == 1f64, &quot;Our classifier isn&#39;t very good!&quot;);
//! ```
</span><span class="kw">use </span>linalg::{Matrix, BaseMatrix};
<span class="kw">use </span>linalg::Vector;
<span class="kw">use </span>learning::toolkit::kernel::{Kernel, SquaredExp};
<span class="kw">use </span>learning::{LearningResult, SupModel};
<span class="kw">use </span>learning::error::{Error, ErrorKind};
<span class="kw">use </span>rand;
<span class="kw">use </span>rand::Rng;
<span class="doccomment">/// Support Vector Machine
</span><span class="attribute">#[derive(Debug)]
</span><span class="kw">pub struct </span>SVM&lt;K: Kernel&gt; {
ker: K,
alpha: <span class="prelude-ty">Option</span>&lt;Vector&lt;f64&gt;&gt;,
train_inputs: <span class="prelude-ty">Option</span>&lt;Matrix&lt;f64&gt;&gt;,
train_targets: <span class="prelude-ty">Option</span>&lt;Vector&lt;f64&gt;&gt;,
lambda: f64,
<span class="doccomment">/// Number of iterations for training.
</span><span class="kw">pub </span>optim_iters: usize,
}
<span class="doccomment">/// The default Support Vector Machine.
///
/// The defaults are:
///
/// - `ker` = `SquaredExp::default()`
/// - `lambda` = `0.3`
/// - `optim_iters` = `100`
</span><span class="kw">impl </span>Default <span class="kw">for </span>SVM&lt;SquaredExp&gt; {
<span class="kw">fn </span>default() -&gt; SVM&lt;SquaredExp&gt; {
SVM {
ker: SquaredExp::default(),
alpha: <span class="prelude-val">None</span>,
train_inputs: <span class="prelude-val">None</span>,
train_targets: <span class="prelude-val">None</span>,
lambda: <span class="number">0.3f64</span>,
optim_iters: <span class="number">100</span>,
}
}
}
<span class="kw">impl</span>&lt;K: Kernel&gt; SVM&lt;K&gt; {
<span class="doccomment">/// Constructs an untrained SVM with specified
/// kernel and lambda which determins the hardness
/// of the margin.
///
/// # Examples
///
/// ```
/// use rusty_machine::learning::svm::SVM;
/// use rusty_machine::learning::toolkit::kernel::SquaredExp;
///
/// let _ = SVM::new(SquaredExp::default(), 0.3);
/// ```
</span><span class="kw">pub fn </span>new(ker: K, lambda: f64) -&gt; SVM&lt;K&gt; {
SVM {
ker: ker,
alpha: <span class="prelude-val">None</span>,
train_inputs: <span class="prelude-val">None</span>,
train_targets: <span class="prelude-val">None</span>,
lambda: lambda,
optim_iters: <span class="number">100</span>,
}
}
}
<span class="kw">impl</span>&lt;K: Kernel&gt; SVM&lt;K&gt; {
<span class="doccomment">/// Construct a kernel matrix
</span><span class="kw">fn </span>ker_mat(<span class="kw-2">&amp;</span><span class="self">self</span>, m1: <span class="kw-2">&amp;</span>Matrix&lt;f64&gt;, m2: <span class="kw-2">&amp;</span>Matrix&lt;f64&gt;) -&gt; LearningResult&lt;Matrix&lt;f64&gt;&gt; {
<span class="kw">if </span>m1.cols() != m2.cols() {
<span class="prelude-val">Err</span>(Error::new(ErrorKind::InvalidState,
<span class="string">&quot;Inputs to kernel matrices have different column counts.&quot;</span>))
} <span class="kw">else </span>{
<span class="kw">let </span>dim1 = m1.rows();
<span class="kw">let </span>dim2 = m2.rows();
<span class="kw">let </span><span class="kw-2">mut </span>ker_data = Vec::with_capacity(dim1 * dim2);
ker_data.extend(m1.row_iter().flat_map(|row1| {
m2.row_iter()
.map(<span class="kw">move </span>|row2| <span class="self">self</span>.ker.kernel(row1.raw_slice(), row2.raw_slice()))
}));
<span class="prelude-val">Ok</span>(Matrix::new(dim1, dim2, ker_data))
}
}
}
<span class="doccomment">/// Train the model using the Pegasos algorithm and
/// predict the model output from new data.
</span><span class="kw">impl</span>&lt;K: Kernel&gt; SupModel&lt;Matrix&lt;f64&gt;, Vector&lt;f64&gt;&gt; <span class="kw">for </span>SVM&lt;K&gt; {
<span class="kw">fn </span>predict(<span class="kw-2">&amp;</span><span class="self">self</span>, inputs: <span class="kw-2">&amp;</span>Matrix&lt;f64&gt;) -&gt; LearningResult&lt;Vector&lt;f64&gt;&gt; {
<span class="kw">let </span>ones = Matrix::&lt;f64&gt;::ones(inputs.rows(), <span class="number">1</span>);
<span class="kw">let </span>full_inputs = ones.hcat(inputs);
<span class="kw">if let </span>(<span class="kw-2">&amp;</span><span class="prelude-val">Some</span>(<span class="kw-2">ref </span>alpha), <span class="kw-2">&amp;</span><span class="prelude-val">Some</span>(<span class="kw-2">ref </span>train_inputs), <span class="kw-2">&amp;</span><span class="prelude-val">Some</span>(<span class="kw-2">ref </span>train_targets)) =
(<span class="kw-2">&amp;</span><span class="self">self</span>.alpha, <span class="kw-2">&amp;</span><span class="self">self</span>.train_inputs, <span class="kw-2">&amp;</span><span class="self">self</span>.train_targets) {
<span class="kw">let </span>ker_mat = <span class="self">self</span>.ker_mat(<span class="kw-2">&amp;</span>full_inputs, train_inputs)<span class="question-mark">?</span>;
<span class="kw">let </span>weight_vec = alpha.elemul(train_targets) / <span class="self">self</span>.lambda;
<span class="kw">let </span>plane_dist = ker_mat * weight_vec;
<span class="prelude-val">Ok</span>(plane_dist.apply(<span class="kw-2">&amp;</span>|d| d.signum()))
} <span class="kw">else </span>{
<span class="prelude-val">Err</span>(Error::new_untrained())
}
}
<span class="kw">fn </span>train(<span class="kw-2">&amp;mut </span><span class="self">self</span>, inputs: <span class="kw-2">&amp;</span>Matrix&lt;f64&gt;, targets: <span class="kw-2">&amp;</span>Vector&lt;f64&gt;) -&gt; LearningResult&lt;()&gt; {
<span class="kw">let </span>n = inputs.rows();
<span class="kw">let </span><span class="kw-2">mut </span>rng = rand::thread_rng();
<span class="kw">let </span><span class="kw-2">mut </span>alpha = <span class="macro">vec!</span>[<span class="number">0f64</span>; n];
<span class="kw">let </span>ones = Matrix::&lt;f64&gt;::ones(inputs.rows(), <span class="number">1</span>);
<span class="kw">let </span>full_inputs = ones.hcat(inputs);
<span class="kw">for </span>t <span class="kw">in </span><span class="number">0</span>..<span class="self">self</span>.optim_iters {
<span class="kw">let </span>i = rng.gen_range(<span class="number">0</span>..n);
<span class="kw">let </span>row_i = full_inputs.select_rows(<span class="kw-2">&amp;</span>[i]);
<span class="kw">let </span>sum = full_inputs.row_iter()
.fold(<span class="number">0f64</span>, |sum, row| sum + <span class="self">self</span>.ker.kernel(row_i.data(), row.raw_slice())) *
targets[i] / (<span class="self">self</span>.lambda * (t <span class="kw">as </span>f64));
<span class="kw">if </span>sum &lt; <span class="number">1f64 </span>{
alpha[i] += <span class="number">1f64</span>;
}
}
<span class="self">self</span>.alpha = <span class="prelude-val">Some</span>(Vector::new(alpha) / (<span class="self">self</span>.optim_iters <span class="kw">as </span>f64));
<span class="self">self</span>.train_inputs = <span class="prelude-val">Some</span>(full_inputs);
<span class="self">self</span>.train_targets = <span class="prelude-val">Some</span>(targets.clone());
<span class="prelude-val">Ok</span>(())
}
}
</code></pre></div>
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