chore: release v1.0.2

src/statistic/common.rs

@@ -14,3 +14,57 @@ pub(super) fn linreg(window: &[f64]) -> (f64, f64) {
     let intercept = (sum_y - slope * sum_x) / n;
     (slope, intercept)
 }
+
+pub(crate) fn rolling_linreg_apply<F>(prices: &[f64], timeperiod: usize, mut map: F) -> Vec<f64>
+where
+    F: FnMut(f64, f64) -> f64,
+{
+    let n = prices.len();
+    let mut result = vec![f64::NAN; n];
+    if timeperiod == 0 || n < timeperiod {
+        return result;
+    }
+
+    if prices.iter().any(|value| !value.is_finite()) {
+        for end in (timeperiod - 1)..n {
+            let window = &prices[(end + 1 - timeperiod)..=end];
+            let (slope, intercept) = linreg(window);
+            result[end] = map(slope, intercept);
+        }
+        return result;
+    }
+
+    let period = timeperiod as f64;
+    let last_x = (timeperiod - 1) as f64;
+    let sum_x = last_x * period / 2.0;
+    let sum_x2 = last_x * period * (2.0 * period - 1.0) / 6.0;
+    let denom = period * sum_x2 - sum_x * sum_x;
+
+    let mut sum_y = prices[..timeperiod].iter().sum::<f64>();
+    let mut sum_xy = prices[..timeperiod]
+        .iter()
+        .enumerate()
+        .map(|(idx, &value)| idx as f64 * value)
+        .sum::<f64>();
+
+    for end in (timeperiod - 1)..n {
+        let slope = if denom != 0.0 {
+            (period * sum_xy - sum_x * sum_y) / denom
+        } else {
+            0.0
+        };
+        let intercept = (sum_y - slope * sum_x) / period;
+        result[end] = map(slope, intercept);
+
+        if end + 1 < n {
+            let outgoing = prices[end + 1 - timeperiod];
+            let incoming = prices[end + 1];
+            let prev_sum_y = sum_y;
+
+            sum_y = prev_sum_y - outgoing + incoming;
+            sum_xy = sum_xy - (prev_sum_y - outgoing) + last_x * incoming;
+        }
+    }
+
+    result
+}