# Yew Charting Library
`yew-chart` is a collection of components that can be assembled to form charts
for the [Yew framework](https://github.com/yewstack/yew).
Here is a soil moisture/rainfall chart that has been produced using this library:
Here's another chart produced by this library, representing what is known as ["Delta-T"](http://www.bom.gov.au/lam/deltat.shtml):
By leveraging these SVG-based components many types of charts can be formed
with a great deal of flexibility. The library is intended as a toolkit that
provides conveniences for rendering chart primitives. These primitives can
be regarded at a similar level as SVG's primitives i.e. lines, polygons etc.
## Example Plots
Two basic projects are given in the `examples` folder.
### Line Chart
`examples/basic` is configured to output a basic line chart:
...and here's the entire Yew component that was used to generate it:
```rust
const WIDTH: f32 = 533.0;
const HEIGHT: f32 = 300.0;
const MARGIN: f32 = 50.0;
const TICK_LENGTH: f32 = 10.0;
#[function_component(App)]
fn app() -> Html {
let end_date = Utc::now();
let start_date = end_date.sub(Duration::days(4));
let timespan = start_date..end_date;
let circle_text_labeller = Rc::from(series::circle_text_label("Label")) as Rc;
let data_set = Rc::new(vec![
(start_date.timestamp_millis(), 1.0, None),
(
start_date.add(Duration::days(1)).timestamp_millis(),
4.0,
None,
),
(
start_date.add(Duration::days(2)).timestamp_millis(),
3.0,
None,
),
(
start_date.add(Duration::days(3)).timestamp_millis(),
2.0,
None,
),
(
start_date.add(Duration::days(4)).timestamp_millis(),
5.0,
Some(circle_text_labeller),
),
]);
let h_scale = Rc::new(TimeScale::new(timespan, Duration::days(1))) as Rc>;
let v_scale = Rc::new(LinearScale::new(0.0..5.0, 1.0)) as Rc>;
let tooltip = Rc::from(series::y_tooltip()) as Rc>;
html! {
}
}
```
> If passing `SeriesData` around via `Props`, you'll need to provide a `PartialEq` implementation. Rust won't be able to derive one
> automatically for you as `SeriesData` holds a closure that cannot be compared. This doesn't end up being a problem though as
> should be performing an explicit pointer comparison when comparing `Rc` based values anyway; `Rc` contained references are immutable.
> `Rc::ptr_eq` is your friend in this scenario.
>
> That all said, you probably won't be passing `SeriesData` around via props, but some other `Rc` of a model oriented data type
> which is to be mapped to it. Using `ptr_eq` is still the way to go there though as you'll get performance benefits.
### Bar Chart
Using the same Yew view method code as above, `series_type` within the `Series` tag can be edited to display a bar chart instead by using the `Bar` keys.
```rust
```
The bar chart can also be made to 'drop' instead of 'rise' with the enum variant `BarType`. This is particularly helpful if using negative axis values, where the bars are dropping from `y = 0` or similar.
When the `BarType` is set to `Drop`, the same data from above produces the following graph.
As seen, the bars are set to go from the selected side _to_ the datapoint. Since the axis range is from `0.0` to `5.0`, and the first point is at `(26-Mar, 1.0)`, the bar drops from `5.0` to `1.0`.
```rust
```
One final example of this is in using a negative scale and negative values. In the following graph, the axis ranges from `-5.0` to `0.0`, and the first point is `(01-Apr, -1.0)`.
