Add examples for distribution helpers

examples/distributions.rs

@@ -0,0 +1,66 @@
+use rustframe::compute::stats::{binomial_cdf, binomial_pmf, normal_cdf, normal_pdf, poisson_pmf};
+use rustframe::matrix::Matrix;
+
+/// Demonstrates some probability distribution helpers.
+fn main() {
+    normal_example();
+    println!("\n-----\n");
+    binomial_example();
+    println!("\n-----\n");
+    poisson_example();
+}
+
+fn normal_example() {
+    println!("Normal distribution\n-------------------");
+    let x = Matrix::from_vec(vec![0.0, 1.0], 1, 2);
+    let pdf = normal_pdf(x.clone(), 0.0, 1.0);
+    let cdf = normal_cdf(x, 0.0, 1.0);
+    println!("pdf : {:?}", pdf.data());
+    println!("cdf : {:?}", cdf.data());
+}
+
+fn binomial_example() {
+    println!("Binomial distribution\n---------------------");
+    let k = Matrix::from_vec(vec![0_u64, 1, 2], 1, 3);
+    let pmf = binomial_pmf(4, k.clone(), 0.5);
+    let cdf = binomial_cdf(4, k, 0.5);
+    println!("pmf : {:?}", pmf.data());
+    println!("cdf : {:?}", cdf.data());
+}
+
+fn poisson_example() {
+    println!("Poisson distribution\n--------------------");
+    let k = Matrix::from_vec(vec![0_u64, 1, 2], 1, 3);
+    let pmf = poisson_pmf(3.0, k);
+    println!("pmf : {:?}", pmf.data());
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_normal_example() {
+        let x = Matrix::from_vec(vec![0.0, 1.0], 1, 2);
+        let pdf = normal_pdf(x.clone(), 0.0, 1.0);
+        let cdf = normal_cdf(x, 0.0, 1.0);
+        assert!((pdf.get(0, 0) - 0.39894228).abs() < 1e-6);
+        assert!((cdf.get(0, 1) - 0.8413447).abs() < 1e-6);
+    }
+
+    #[test]
+    fn test_binomial_example() {
+        let k = Matrix::from_vec(vec![0_u64, 1, 2], 1, 3);
+        let pmf = binomial_pmf(4, k.clone(), 0.5);
+        let cdf = binomial_cdf(4, k, 0.5);
+        assert!((pmf.get(0, 2) - 0.375).abs() < 1e-6);
+        assert!((cdf.get(0, 2) - 0.6875).abs() < 1e-6);
+    }
+
+    #[test]
+    fn test_poisson_example() {
+        let k = Matrix::from_vec(vec![0_u64, 1, 2], 1, 3);
+        let pmf = poisson_pmf(3.0, k);
+        assert!((pmf.get(0, 1) - 3.0_f64 * (-3.0_f64).exp()).abs() < 1e-6);
+    }
+}