1 files changed, 137 insertions, 0 deletions
diff --git a/examples/iris.rs b/examples/iris.rs
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+++ b/examples/iris.rs
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+///
+/// This example parses, sorts and groups the iris dataset
+/// and does some simple manipulations.
+///
+/// Iterators and itertools functionality are used throughout.
+
+use itertools::Itertools;
+use std::collections::HashMap;
+use std::iter::repeat;
+use std::num::ParseFloatError;
+use std::str::FromStr;
+
+static DATA: &'static str = include_str!("iris.data");
+
+#[derive(Clone, Debug)]
+struct Iris {
+    name: String,
+    data: [f32; 4],
+}
+
+#[derive(Clone, Debug)]
+enum ParseError {
+    Numeric(ParseFloatError),
+    Other(&'static str),
+}
+
+impl From<ParseFloatError> for ParseError {
+    fn from(err: ParseFloatError) -> Self {
+        ParseError::Numeric(err)
+    }
+}
+
+/// Parse an Iris from a comma-separated line
+impl FromStr for Iris {
+    type Err = ParseError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut iris = Iris { name: "".into(), data: [0.; 4] };
+        let mut parts = s.split(",").map(str::trim);
+
+        // using Iterator::by_ref()
+        for (index, part) in parts.by_ref().take(4).enumerate() {
+            iris.data[index] = part.parse::<f32>()?;
+        }
+        if let Some(name) = parts.next() {
+            iris.name = name.into();
+        } else {
+            return Err(ParseError::Other("Missing name"))
+        }
+        Ok(iris)
+    }
+}
+
+fn main() {
+    // using Itertools::fold_results to create the result of parsing
+    let irises = DATA.lines()
+                     .map(str::parse)
+                     .fold_results(Vec::new(), |mut v, iris: Iris| {
+                         v.push(iris);
+                         v
+                     });
+    let mut irises = match irises {
+        Err(e) => {
+            println!("Error parsing: {:?}", e);
+            std::process::exit(1);
+        }
+        Ok(data) => data,
+    };
+
+    // Sort them and group them
+    irises.sort_by(|a, b| Ord::cmp(&a.name, &b.name));
+
+    // using Iterator::cycle()
+    let mut plot_symbols = "+ox".chars().cycle();
+    let mut symbolmap = HashMap::new();
+
+    // using Itertools::group_by
+    for (species, species_group) in &irises.iter().group_by(|iris| &iris.name) {
+        // assign a plot symbol
+        symbolmap.entry(species).or_insert_with(|| {
+            plot_symbols.next().unwrap()
+        });
+        println!("{} (symbol={})", species, symbolmap[species]);
+
+        for iris in species_group {
+            // using Itertools::format for lazy formatting
+            println!("{:>3.1}", iris.data.iter().format(", "));
+        }
+
+    }
+
+    // Look at all combinations of the four columns
+    //
+    // See https://en.wikipedia.org/wiki/Iris_flower_data_set
+    //
+    let n = 30; // plot size
+    let mut plot = vec![' '; n * n];
+
+    // using Itertools::tuple_combinations
+    for (a, b) in (0..4).tuple_combinations() {
+        println!("Column {} vs {}:", a, b);
+
+        // Clear plot
+        //
+        // using std::iter::repeat;
+        // using Itertools::set_from
+        plot.iter_mut().set_from(repeat(' '));
+
+        // using Itertools::minmax
+        let min_max = |data: &[Iris], col| {
+            data.iter()
+                .map(|iris| iris.data[col])
+                .minmax()
+                .into_option()
+                .expect("Can't find min/max of empty iterator")
+        };
+        let (min_x, max_x) = min_max(&irises, a);
+        let (min_y, max_y) = min_max(&irises, b);
+
+        // Plot the data points
+        let round_to_grid = |x, min, max| ((x - min) / (max - min) * ((n - 1) as f32)) as usize;
+        let flip = |ix| n - 1 - ix; // reverse axis direction
+
+        for iris in &irises {
+            let ix = round_to_grid(iris.data[a], min_x, max_x);
+            let iy = flip(round_to_grid(iris.data[b], min_y, max_y));
+            plot[n * iy + ix] = symbolmap[&iris.name];
+        }
+
+        // render plot
+        //
+        // using Itertools::join
+        for line in plot.chunks(n) {
+            println!("{}", line.iter().join(" "))
+        }
+    }
+}