diff --git a/src/series/num_series.rs b/src/series/num_series.rs
index 9c23345..dd53f73 100644
--- a/src/series/num_series.rs
+++ b/src/series/num_series.rs
@@ -1,21 +1,121 @@
+use super::Series;
+
 pub trait NumSeries {
-    fn sum(&self) -> f64;
-    fn product(&self) -> f64;
-    fn mean(&self) -> f64;
-    fn median(&self) -> f64;
-    fn mode(&self) -> f64;
-    fn std_dev(&self) -> f64;
-    fn min(&self) -> f64;
-
-    fn add(&self) -> f64;
-    fn sub(&self) -> f64;
-    fn mul(&self) -> f64;
-    fn div(&self) -> f64;
-
-    fn corr(&self) -> f64; // calculates correlation matrix
-    fn cov(&self) -> f64; // calculates covariance matrix
-    fn max(&self) -> f64;
+    fn sum(&self) -> Option<f64>;
+    fn product(&self) -> Option<f64>;
+    fn mean(&self) -> Option<f64>;
+    fn median(&self) -> Option<f64>;
+    fn mode(&self) -> Option<f64>;
+    fn std_dev(&self) -> Option<f64>;
+    fn min(&self) -> Option<f64>;
+
+    fn add(&self) -> Option<f64>;
+    fn sub(&self) -> Option<f64>;
+    fn mul(&self) -> Option<f64>;
+    fn div(&self) -> Option<f64>;
+
+    fn corr(&self) -> Option<f64>; // calculates correlation matrix
+    fn cov(&self) -> Option<f64>; // calculates covariance matrix
+    fn max(&self) -> Option<f64>;
     
     fn drop_na(&self); // clears null/empty values
     fn fill_na(&self); // fill empty values
+}
+
+impl NumSeries for Series {
+    fn sum(&self) -> Option<f64> {
+        if let Series::Num(ref vec) = &self {
+            Some(vec.iter().sum::<f64>())
+        } else {
+            None
+        }
+    }
+
+    fn product(&self) -> Option<f64> {
+        if let Series::Num(ref vec) = &self {
+            Some(vec.iter().product::<f64>())
+        } else {
+            None
+        }
+    }
+
+    fn mean(&self) -> Option<f64> {
+        if let Series::Num(ref vec) = &self {
+            Some(vec.iter().sum::<f64>() / vec.len() as f64)
+        } else {
+            None
+        }
+    }
+
+    fn median(&self) -> Option<f64> {
+        todo!()
+    }
+
+    fn mode(&self) -> Option<f64> {
+        todo!()
+    }
+
+    fn std_dev(&self) -> Option<f64> {
+        todo!()
+    }
+
+    fn min(&self) -> Option<f64> {
+        if let Series::Num(ref vec) = &self {
+            if vec.len() == 0 {
+                return None;
+            }
+
+            let mut vec = vec.clone();
+            vec.sort_by(|a, b| a.partial_cmp(b).unwrap());
+            Some(vec[0])
+        } else {
+            None
+        }
+    }
+
+    fn max(&self) -> Option<f64> {
+        if let Series::Num(ref vec) = &self {
+            if vec.len() == 0 {
+                return None;
+            }
+
+            let mut vec = vec.clone();
+            vec.sort_by(|a, b| a.partial_cmp(b).unwrap());
+            Some(vec[vec.len() - 1])
+        } else {
+            None
+        }
+    }
+
+    fn add(&self) -> Option<f64> {
+        todo!()
+    }
+
+    fn sub(&self) -> Option<f64> {
+        todo!()
+    }
+
+    fn mul(&self) -> Option<f64> {
+        todo!()
+    }
+
+    fn div(&self) -> Option<f64> {
+        todo!()
+    }
+
+    fn corr(&self) -> Option<f64> {
+        todo!()
+    }
+
+    fn cov(&self) -> Option<f64> {
+        todo!()
+    }
+
+    fn drop_na(&self) {
+        todo!()
+    }
+
+    fn fill_na(&self) {
+        todo!()
+    }
 }
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