Add section about tweaking labels

README.md

@@ -1,2 +1,3 @@
-# guide
-The Plotters Guide
+# Plotters Guide
+
+This repository is found rendered [here](https://plotters-rs.github.io/book/intro/introduction.html).

markdown/tweak/aixs_mesh_labels.md

@@ -1,8 +1,88 @@
 # Axis, mesh and label tweaks
 
+`ChartBuilder`'s `build_cartesian_2d()` returns a ChartContext. The ChartContext gives you the ability to configure the mesh and axis of your plots using `configure_mesh`. For all implementations, see [the docs](https://docs.rs/plotters/latest/plotters/chart/struct.MeshStyle.html). 
+
+## Lables
+
+### Label formatters
+
+Default labels for the axis are the elements of the ranges given as parameters to `ChartBuilder`'s `build_cartesian_2d()` or `build_cartesian_3d()`. To customize the labels, you need to provide a formatting function.
+
+```rust
+use plotters::prelude::*;
+fn main() {
+    let root = BitMapBackend::new("images/label-formatters.png", (640, 480)).into_drawing_area();
+
+    root.fill(&WHITE).unwrap();
+
+    let mut chart = ChartBuilder::on(&root)
+        .margin(15)
+        .set_label_area_size(LabelAreaPosition::Left, 30)
+        .set_label_area_size(LabelAreaPosition::Bottom, 30)
+        .build_cartesian_2d(0..5, 0..5)
+        .unwrap();
+
+    let x_labels = ["Zero", "One", "Two", "Three", "Four", "Five"];
+
+    chart
+        .configure_mesh()
+        .x_label_formatter(&|x| x_labels[*x as usize].to_string())
+        .draw()
+        .unwrap();
+}
+```
+![label-formatters](../../images/label-formatters.png)
+
+### Segmented values
+
+If you want custom labels for your segmented values, you could provide a formatting function like: 
+
+```rust
+use plotters::prelude::*;
+fn main() {
+    let root = BitMapBackend::new("images/label-formatters-segment-value.png", (640, 480)).into_drawing_area();
+
+    root.fill(&WHITE).unwrap();
+
+    let mut chart = ChartBuilder::on(&root)
+        .margin(15)
+        .set_label_area_size(LabelAreaPosition::Left, 30)
+        .set_label_area_size(LabelAreaPosition::Bottom, 30)
+        .build_cartesian_2d((0..5).into_segmented(), 0..5)
+        .unwrap();
+
+    let x_labels = ["Zero", "One", "Two", "Three", "Four", "Five"];
+
+    chart 
+        .configure_mesh()
+        .x_label_formatter(&|x| match x {
+            SegmentValue::CenterOf(a) | SegmentValue::Exact(a) => x_labels[*a as usize].to_string(),
+            _a => "".to_string(),
+        })
+        .draw()
+        .unwrap();
+
+    let values = [1, 0, 3, 5, 2, 3];
+
+    // Drawing the actual bars as well in order for the labels to make more sense: 
+    chart
+        .draw_series((0..).zip(values.iter()).map(|(x, y)| {
+            let x0 = SegmentValue::Exact(x);
+            let x1 = SegmentValue::Exact(x + 1);
+            let mut bar = Rectangle::new([(x0, 0), (x1, *y)], RED.filled());
+            bar.set_margin(0, 0, 5, 5);
+            bar
+        }))
+        .unwrap();
+}
+```
+![label-formatters-segment-value](../../images/label-formatters-segment-value.png)
+
+## TODO:
+
 - Adjust number of tick marks on axis
 - Changing axis, labels and mesh styles
 - Partially visible axis
-- Label formatters
 - Inward labels
 - Log scale axis
+