change to lla_to_utm_zone_number which returns u8

polars_coord_transforms/__init__.py

@@ -78,10 +78,10 @@ def lla_to_utm(self) -> pl.Expr:
             is_elementwise=True
         )
 
-    def lla_to_utm_zone(self) -> pl.Expr:
+    def lla_to_utm_zone_number(self) -> pl.Expr:
         return self._expr.register_plugin(
             lib=lib,
-            symbol="lla_to_utm_zone",
+            symbol="lla_to_utm_zone_number",
             is_elementwise=True
         )
 

src/coord_transforms.rs

@@ -1,6 +1,6 @@
 extern crate nalgebra as na;
 
-use utm::{to_utm_wgs84_no_zone, lat_lon_to_zone_number, lat_to_zone_letter};
+use utm::{to_utm_wgs84_no_zone, lat_lon_to_zone_number};
 use na::{Vector3, Vector4, Quaternion, UnitQuaternion, Rotation3};
 use map_3d::{ecef2geodetic, geodetic2ecef, rad2deg, deg2rad, Ellipsoid};
 
@@ -37,10 +37,9 @@ pub fn lla_to_ecef_elementwise(lon: f64, lat: f64, alt: f64) -> (f64, f64, f64)
 
 
 
-pub fn lla_to_utm_zone_elementwise(lon: f64, lat: f64) -> (u8, char) {
+pub fn lla_to_utm_zone_number_elementwise(lon: f64, lat: f64) -> u8 {
     let zone_number = lat_lon_to_zone_number(lat, lon);
-    let zone_letter = lat_to_zone_letter(lat).expect("Unable to find UTM zone letter from latitude!");
-    (zone_number, zone_letter)
+    zone_number
 }   
 
 

src/expressions.rs

@@ -1,11 +1,8 @@
 use itertools::Itertools;
-use polars_core::chunked_array::builder::Utf8ChunkedBuilderCow;
 use polars::prelude::*;
 use polars::datatypes::DataType;
 use pyo3_polars::derive::polars_expr;
 
-use std::borrow::Cow;
-
 use itertools::izip;
 use serde::Deserialize;
 
@@ -457,48 +454,34 @@ fn lla_to_utm(inputs: &[Series]) -> PolarsResult<Series> {
 }   
 
 
-fn utm_zone_output(_: &[Field]) -> PolarsResult<Field> {
-    let v: Vec<Field> = vec![
-        Field::new("utm_zone_number", DataType::UInt8),
-        Field::new("utm_zone_letter", DataType::Utf8),
-    ];
-    Ok(Field::new("utm_zone", DataType::Struct(v)))
-}
 
-#[polars_expr(output_type_func=utm_zone_output)]
-fn lla_to_utm_zone(inputs: &[Series]) -> PolarsResult<Series> {
+#[polars_expr(output_type=UInt8)]
+fn lla_to_utm_zone_number(inputs: &[Series]) -> PolarsResult<Series> {
 
     let coords_ca = inputs[0].struct_()?;
     let (lon_ser, lat_ser, _alt_ser) = unpack_xyz(coords_ca, true);
 
 
     let mut utm_number_cb: PrimitiveChunkedBuilder<UInt8Type> =
         PrimitiveChunkedBuilder::new("utm_zone_number", coords_ca.len());
-    let mut utm_letter_cb: Utf8ChunkedBuilderCow = Utf8ChunkedBuilderCow::new("utm_zone_letter", coords_ca.len());
 
     for (lon_op, lat_op) in izip!(
         lon_ser.f64()?,
         lat_ser.f64()?,
     ) {
         match (lon_op, lat_op) {
             (Some(lon), Some(lat)) => {
-                let (utm_number, utm_letter,) = lla_to_utm_zone_elementwise(lon, lat);
+                let utm_number = lla_to_utm_zone_number_elementwise(lon, lat);
                 utm_number_cb.append_value(utm_number);
-                utm_letter_cb.append_value(Cow::Owned(String::from(utm_letter)));
-
             },
             _ => {
                 utm_number_cb.append_null();
-                utm_letter_cb.append_null();
 
             }
         }
     }
     let ser_utm_number = utm_number_cb.finish().into_series();   
-    let ser_utm_letter = utm_letter_cb.finish().into_series();    
-
-    let out_chunked: StructChunked = StructChunked::new("utm_zone", &[ser_utm_number, ser_utm_letter])?;
-    Ok(out_chunked.into_series())
+    Ok(ser_utm_number)
 
 }