Added from_coordinates method to SparseVector

src/sparsevec.rs

@@ -48,6 +48,23 @@ impl SparseVector {
         }
     }
 
+    /// Creates a sparse vector from coordinates.
+    pub fn from_coordinates<I: IntoIterator<Item = (i32, f32)>>(
+        iter: I,
+        dim: usize,
+    ) -> SparseVector {
+        let mut elements: Vec<(i32, f32)> = iter.into_iter().collect();
+        elements.sort_by_key(|v| v.0);
+        let indices: Vec<i32> = elements.iter().map(|v| v.0).collect();
+        let values: Vec<f32> = elements.iter().map(|v| v.1).collect();
+
+        SparseVector {
+            dim,
+            indices,
+            values,
+        }
+    }
+
     /// Returns the sparse vector as a `Vec<f32>`.
     pub fn to_vec(&self) -> Vec<f32> {
         let mut vec = vec![0.0; self.dim];
@@ -91,13 +108,28 @@ impl SparseVector {
 #[cfg(test)]
 mod tests {
     use crate::SparseVector;
+    use std::collections::HashMap;
 
     #[test]
     fn test_from_dense() {
         let vec = SparseVector::from_dense(&[1.0, 0.0, 2.0, 0.0, 3.0, 0.0]);
         assert_eq!(vec![1.0, 0.0, 2.0, 0.0, 3.0, 0.0], vec.to_vec());
     }
 
+    #[test]
+    fn test_from_coo_map() {
+        let elements = HashMap::from([(0, 1.0), (2, 2.0), (4, 3.0)]);
+        let vec = SparseVector::from_coordinates(elements, 6);
+        assert_eq!(vec![1.0, 0.0, 2.0, 0.0, 3.0, 0.0], vec.to_vec());
+    }
+
+    #[test]
+    fn test_from_coo_vec() {
+        let elements = vec![(0, 1.0), (2, 2.0), (4, 3.0)];
+        let vec = SparseVector::from_coordinates(elements, 6);
+        assert_eq!(vec![1.0, 0.0, 2.0, 0.0, 3.0, 0.0], vec.to_vec());
+    }
+
     #[test]
     fn test_to_vec() {
         let vec = SparseVector::new(6, vec![0, 2, 4], vec![1.0, 2.0, 3.0]);