Add Blackman window

sci-rs/src/signal/windows/blackman.rs

@@ -0,0 +1,121 @@
+use super::GeneralCosine;
+use super::{extend, len_guard, truncate};
+use nalgebra::RealField;
+use num_traits::{real::Real, Float};
+
+#[cfg(feature = "alloc")]
+use super::GetWindow;
+#[cfg(feature = "alloc")]
+use alloc::{vec, vec::Vec};
+
+/// Collection of arguments for window `Blackman` for use in [GetWindow].
+#[derive(Debug, Clone, PartialEq)]
+pub struct Blackman {
+    /// Number of points in the output window. If zero, an empty array is returned in [GetWindow].
+    pub m: usize,
+    /// Whether the window is symmetric.
+    ///
+    /// When true, generates a symmetric window, for use in filter design.  
+    /// When false, generates a periodic window, for use in spectral analysis.
+    pub sym: bool,
+}
+
+impl Blackman {
+    /// Returns a Blackman struct.  
+    ///
+    /// # Parameters
+    /// * `m`:  
+    ///     Number of points in the output window. If zero, an empty array is returned.  
+    /// * `sym`:  
+    ///     When true, generates a symmetric window, for use in filter design.  
+    ///     When false, generates a periodic window, for use in spectral analysis.
+    pub fn new(m: usize, sym: bool) -> Self {
+        Blackman { m, sym }
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl GetWindow for Blackman {
+    /// Return a window of type: Blackman.
+    ///
+    /// The Blackman window is a taper formed by using the first three terms of a summation of
+    /// cosines. It was designed to have close to the minimal leakage possible. It is close to
+    /// optimal, only slightly worse than a Kaiser window.
+    ///
+    /// # Parameters
+    /// `self`: [Blackman]
+    ///
+    /// # Returns
+    /// `w`: `vec<F>`  
+    ///     The window, with the maximum value normalized to 1 (though the value 1 does not appear
+    ///     if `M` is even and `sym` is True).
+    ///
+    /// # Example
+    /// ```
+    /// use sci_rs::signal::windows::{Blackman, GetWindow};
+    ///
+    /// let nx = 8;
+    /// let b = Blackman::new(nx, true);
+    /// ```
+    ///
+    /// # References
+    /// <https://docs.scipy.org/doc/scipy/reference/generated/scipy.signal.windows.blackman.html>
+    #[cfg(feature = "alloc")]
+    fn get_window<F>(&self) -> Vec<F>
+    where
+        F: Real + Float + RealField,
+    {
+        GeneralCosine::new(
+            self.m,
+            [0.42, 0.50, 0.08]
+                .into_iter()
+                .map(|n| F::from(n).unwrap())
+                .collect(),
+            self.sym,
+        )
+        .get_window()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use approx::assert_abs_diff_eq;
+
+    #[test]
+    fn blackman_20() {
+        // Created with
+        // >>> from scipy.signal.windows import blackman
+        // >>> blackman(20)
+        let expected = vec![
+            -1.38777878e-17,
+            1.02226199e-02,
+            4.50685843e-02,
+            1.14390287e-01,
+            2.26899356e-01,
+            3.82380768e-01,
+            5.66665187e-01,
+            7.52034438e-01,
+            9.03492728e-01,
+            9.88846031e-01,
+            9.88846031e-01,
+            9.03492728e-01,
+            7.52034438e-01,
+            5.66665187e-01,
+            3.82380768e-01,
+            2.26899356e-01,
+            1.14390287e-01,
+            4.50685843e-02,
+            1.02226199e-02,
+            -1.38777878e-17,
+        ];
+        assert_vec_eq(expected, Blackman::new(20, true).get_window());
+    }
+
+    #[track_caller]
+    fn assert_vec_eq(a: Vec<f64>, b: Vec<f64>) {
+        for (a, b) in a.into_iter().zip(b) {
+            assert_abs_diff_eq!(a, b, epsilon = 1e-6);
+        }
+    }
+}

sci-rs/src/signal/windows/mod.rs

@@ -57,9 +57,11 @@ fn truncate<'a, W>(mut w: Vec<W>, needed: bool) -> Vec<W> {
     w
 }
 
+mod blackman;
 mod boxcar;
 mod general_cosine;
 mod triangle;
+pub use blackman::Blackman;
 pub use boxcar::Boxcar;
 pub use general_cosine::GeneralCosine;
 pub use triangle::Triangle;
@@ -80,7 +82,8 @@ where
     Boxcar(Boxcar),
     /// Triangle window.
     Triangle(Triangle),
-    // Blackman,
+    /// Blackman window
+    Blackman(Blackman),
     // Hamming,
     // Hann,
     // Bartlett,