diff --git a/src/rust_fn/mod.rs b/src/rust_fn/mod.rs
index 8cb36e2..f12d712 100644
--- a/src/rust_fn/mod.rs
+++ b/src/rust_fn/mod.rs
@@ -1,7 +1,7 @@
 use csv::ReaderBuilder;
 use glob::glob;
 use indicatif::ProgressBar;
-use ndarray::{concatenate, stack, Array1, Array2, ArrayView1, ArrayView2, Axis, Slice};
+use ndarray::{Array1, Array2, ArrayView1, ArrayView2, Axis, Slice, concatenate, stack};
 use rayon::prelude::*;
 use std::fs::File;
 use std::path::{Path, PathBuf};
@@ -175,25 +175,32 @@ pub fn read_file(filepath: PathBuf) -> Result<(Array2<f64>, f64, usize)> {
         .delimiter(b' ')
         .has_headers(false)
         .from_reader(file);
-    let data = rdr
-        .records()
-        .collect::<std::result::Result<Vec<csv::StringRecord>, _>>()?
-        .iter()
-        .map(|x| {
-            x.iter()
-                .map(|y| y.parse::<i64>().map_err(ReadError::ParseIntError))
-                .collect::<Result<Vec<i64>>>()
-        })
-        .collect::<Result<Vec<_>>>()?;
-    let length = data.len();
-    let width = data[0].len(); // WARNING: assumes fixed width columns!
-    let mut arr: Array2<f64> = Array2::zeros((length, width));
-    for (data_row, mut arr_row) in data.iter().zip(arr.axis_iter_mut(Axis(0))) {
-        for (data_i, arr_i) in data_row.iter().zip(arr_row.iter_mut()) {
-            *arr_i = *data_i as f64
+
+    let mut flat_data = Vec::new();
+    let mut width = 0;
+    let mut length = 0;
+
+    for result in rdr.records() {
+        let record = result?;
+        length += 1;
+
+        if width == 0 {
+            width = record.len();
+        } else if record.len() != width {
+            return Err(ReadError::MiscError(format!(
+                "Inconsistent row width: expected {}, found {}",
+                width,
+                record.len()
+            )));
+        }
+
+        for field in record.iter() {
+            flat_data.push(field.parse::<f64>()?);
         }
     }
 
+    let arr = Array2::from_shape_vec((length, width), flat_data)?;
+
     Ok((arr, z, length))
 }
 
@@ -236,7 +243,7 @@ mod tests {
     };
     use std::path::PathBuf;
     use tar::Archive;
-    use tempfile::{tempdir, TempDir};
+    use tempfile::{TempDir, tempdir};
     use xz::read::XzDecoder;
 
     const TEST_DATA_FILE: &str = "tests/correct.tar.xz";
@@ -382,12 +389,14 @@ mod tests {
         let true_x = unpack_test_data("correct_x_out.flex").unwrap();
         let mut test_x = Array::range(-1000000., 1000000., 1.);
         test_x.par_map_inplace(rust_fn::correct_x);
-        assert!(true_x
-            .iter()
-            .zip(test_x.iter())
-            .all(|(&x, y): (&f64, &f64)| -> bool {
-                x.ulps_eq(y, f64::default_epsilon(), f64::default_max_ulps())
-            }));
+        assert!(
+            true_x
+                .iter()
+                .zip(test_x.iter())
+                .all(|(&x, y): (&f64, &f64)| -> bool {
+                    x.ulps_eq(y, f64::default_epsilon(), f64::default_max_ulps())
+                })
+        );
     }
 
     #[test]
@@ -405,11 +414,13 @@ mod tests {
         let true_y = unpack_test_data("correct_y_out.flex").unwrap();
         let mut test_y = Array::range(-1000000., 1000000., 1.);
         test_y.par_map_inplace(rust_fn::correct_y);
-        assert!(true_y
-            .iter()
-            .zip(test_y.iter())
-            .all(|(&x, y): (&f64, &f64)| -> bool {
-                x.ulps_eq(y, f64::default_epsilon(), f64::default_max_ulps())
-            }));
+        assert!(
+            true_y
+                .iter()
+                .zip(test_y.iter())
+                .all(|(&x, y): (&f64, &f64)| -> bool {
+                    x.ulps_eq(y, f64::default_epsilon(), f64::default_max_ulps())
+                })
+        );
     }
 }