82 lines
2.8 KiB
Rust
82 lines
2.8 KiB
Rust
use crate::DrawResult;
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use plotters::prelude::*;
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use plotters_canvas::CanvasBackend;
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use web_sys::HtmlCanvasElement;
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use meval::Expr;
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/// Draw power function f(x) = x^power.
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pub fn draw(element: HtmlCanvasElement, func_str: &str, minX: f32, maxX: f32, minY: f32, maxY: f32, num_interval: usize, resolution: i32) -> DrawResult<(impl Fn((i32, i32))-> Option<(f32, f32)>, f32)> {
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let expr: Expr = func_str.parse().unwrap();
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let func = expr.bind("x").unwrap();
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let absrange = (maxX-minX).abs();
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let step = absrange/(num_interval as f32);
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let backend = CanvasBackend::with_canvas_object(element).unwrap();
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let root = backend.into_drawing_area();
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let font: FontDesc = ("sans-serif", 20.0).into();
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root.fill(&WHITE)?;
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let mut chart = ChartBuilder::on(&root)
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.margin(20 as f32)
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.caption(format!("y={}", func_str), font)
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.x_label_area_size(30 as f32)
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.y_label_area_size(30 as f32)
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.build_cartesian_2d(minX..maxX, minY..maxY)?;
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chart.configure_mesh().x_labels(3).y_labels(3).draw()?;
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let data = (1..=resolution)
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.map(|x| (((x as f32/resolution as f32))*(&absrange))+&minX)
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.map(|x| (x, func(x as f64) as f32))
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.filter(|(_,y)| &minY <= y && y <= &maxY);
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chart.draw_series(LineSeries::new(data, &RED))?;
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let (data2, area) = integral_rectangles(minX, minY, maxY, absrange, step, num_interval, &func); // Get rectangle coordinates and the total area
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// Draw rectangles
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chart.draw_series(data2.iter().map(|(x1, x2, y)| Rectangle::new([(*x2, *y), (*x1, 0.0)], &BLUE)))?;
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root.present()?;
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let output = chart.into_coord_trans();
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return Ok(((output), area));
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}
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// Creates and does the math for creating all the rectangles under the graph
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#[inline(always)]
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fn integral_rectangles(minX: f32, minY: f32, maxY: f32, absrange: f32, step: f32, num_interval: usize, func: &dyn Fn(f64) -> f64) -> (Vec<(f32, f32, f32)>, f32) {
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let mut area: f32 = 0.0; // sum of all rectangles' areas
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let mut tmp1: f32; // Top left Y value that's tested
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let mut tmp2: f32; // Top right Y value that's tested
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let mut x2: f32; // X value of the right side of the rectangle
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let mut y: f32; // Y value of the top of the rectangle
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let mut x: f32; // X value of the left side of the rectangle
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let mut data2: Vec<(f32, f32, f32)> = Vec::new();
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for e in 0..num_interval {
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x = ((e as f32)*step)+minX;
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if x > 0.0 {
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x2 = x+step;
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} else {
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x2 = x-step;
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}
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tmp1 = func(x as f64) as f32;
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tmp2 = func(x2 as f64) as f32;
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if tmp2.abs() > tmp1.abs() {
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y = tmp1;
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} else {
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y = tmp2;
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}
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// Add current rectangle's area to the total
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if !y.is_nan() {
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area += y*step;
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data2.push((x, x2, y));
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}
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}
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return (data2, area);
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}
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