diff --git a/polars_xdt/functions.py b/polars_xdt/functions.py
index 7cc9dd7..9a5df09 100644
--- a/polars_xdt/functions.py
+++ b/polars_xdt/functions.py
@@ -858,7 +858,7 @@ def ewma_by_time(
 
             y_0 &= x_0
 
-            \alpha_i &= (\alpha_{i-1} + 1) * \exp(-\lambda(t_i - t_{i-1}))
+            \alpha_i &= (\alpha_{i-1} + 1) \exp(-\lambda(t_i - t_{i-1}))
 
             y_i &= (x_i + \alpha_i y_{i-1}) / (1. + \alpha_i);
 
diff --git a/src/ewma_by_time.rs b/src/ewma_by_time.rs
index 3267ba2..f9abf6f 100644
--- a/src/ewma_by_time.rs
+++ b/src/ewma_by_time.rs
@@ -28,7 +28,7 @@ pub(crate) fn impl_ewma_by_time_float(
         .iter()
         .zip(times.iter())
         .skip(1)
-        .map(|(value, time)| {
+        .for_each(|(value, time)| {
             match (time, value) {
                 (Some(time), Some(value)) => {
                     let delta_time = time - prev_time;
@@ -50,8 +50,7 @@ pub(crate) fn impl_ewma_by_time_float(
                 }
                 _ => out.push(None),
             }
-        })
-        .collect::<Vec<_>>();
+        });
     let arr = PrimitiveArray::<f64>::from(out);
     Float64Chunked::from(arr)
 }