Add function plotting

Author: milliams

src/function.rs

@@ -1,19 +1,45 @@
+use std::f64;
+
 use svg;
 
 use axis;
 use representation::Representation;
 
+use svg_render;
+
 pub struct Function {
-    func: Fn(f64) -> f64,
+    pub data: Vec<(f64, f64)>,
 }
 
 impl Function {
+    pub fn new<F>(f: F, lower: f64, upper: f64) -> Self
+        where F: Fn(f64) -> f64 {
+        let sampling = (upper - lower) / 200.;
+        let samples = (0..).map(|x| lower + (x as f64 * sampling)).take_while(|&x| x <= upper);
+        let values = samples.map(|s| (s, f(s))).collect();
+        Function {
+            data: values,
+        }
+    }
+
     fn x_range(&self) -> (f64, f64) {
-        (0., 1.)
+        let mut min = f64::INFINITY;
+        let mut max = f64::NEG_INFINITY;
+        for &(x, _) in &self.data {
+            min = min.min(x);
+            max = max.max(x);
+        }
+        (min, max)
     }
 
     fn y_range(&self) -> (f64, f64) {
-        (0., 1.)
+        let mut min = f64::INFINITY;
+        let mut max = f64::NEG_INFINITY;
+        for &(_, y) in &self.data {
+            min = min.min(y);
+            max = max.max(y);
+        }
+        (min, max)
     }
 }
 
@@ -32,7 +58,7 @@ impl Representation for Function {
               face_width: f64,
               face_height: f64)
               -> svg::node::element::Group {
-        svg::node::element::Group::new()
+        svg_render::draw_face_line(self, x_axis, y_axis, face_width, face_height)
     }
 
     fn to_text(&self,
@@ -44,3 +70,13 @@ impl Representation for Function {
         "".into()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_function() {
+        let f = Function::new(|x| x*x, 0., 10.);
+    }
+}

src/svg_render.rs

@@ -3,6 +3,7 @@ use svg::node;
 
 use histogram;
 use scatter;
+use function;
 use axis;
 use utils::PairWise;
 
@@ -180,6 +181,36 @@ pub fn draw_face_bars(h: &histogram::Histogram,
     group
 }
 
+pub fn draw_face_line(s: &function::Function,
+                        x_axis: &axis::Axis,
+                        y_axis: &axis::Axis,
+                        face_width: f64,
+                        face_height: f64)
+                        -> node::element::Group {
+    let mut group = node::element::Group::new();
+
+    let mut d: Vec<node::element::path::Command> = vec![];
+    let &(first_x, first_y) = s.data.first().unwrap();
+    let first_x_pos = value_to_face_offset(first_x, x_axis, face_width);
+    let first_y_pos = -value_to_face_offset(first_y, y_axis, face_height);
+    d.push(node::element::path::Command::Move(node::element::path::Position::Absolute, (first_x_pos, first_y_pos).into()));
+    for &(x, y) in &s.data {
+        let x_pos = value_to_face_offset(x, x_axis, face_width);
+        let y_pos = -value_to_face_offset(y, y_axis, face_height);
+        d.push(node::element::path::Command::Line(node::element::path::Position::Absolute, (x_pos, y_pos).into()));
+    }
+
+    let mut path = node::element::path::Data::from(d);
+
+    group.append(node::element::Path::new()
+        .set("fill", "none")
+        .set("stroke", "black")
+        .set("stroke-width", 2)
+        .set("d", path));
+
+    group
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;