summed_area_table
Generic implementation of summed area tables with Rust
You can find more information about summed area tables on Wikipedia.
http://en.wikipedia.org/wiki/Summed_area_table
Basic usage
Dependecies for your cargo.toml
[dependencies]
summed-area-table = "*"
nalgebra = "0.4.0" // this is not needed if you don't want to use nalgebra::DMatImport the required content.
use nalgebra::{DMat}; // this is not needed if you don't want to use nalgebra::DMat
use summed_area_table::{SummedAreaTableSource, SummedAreaTable};Creating a summed area table for a 10x10 matrix filled with ones.
let src: DMat<usize> = DMat::new_ones(10,10);
let table = src.calculate_full_summed_area_table();Getting the sum of a specific area
assert_eq!(100.0, table.get_sum((0,0),(9,9)));
assert_eq!(50.0, table.get_sum((0,0),(9,4)));
assert_eq!(25.0, table.get_sum((0,0),(4,4)));Getting the average of a specific area
assert_eq!(10.0, table.get_average((0,0),(9,9)));
assert_eq!(10.0, table.get_average((0,0),(9,4)));
assert_eq!(10.0, table.get_average((0,0),(4,4)));Custom Data Source
You can implement the SummedAreaTableSource trait for your own types if you want them to have the calculate_summed_area_table() method. All you need, is to implement the SummedAreaTableSource<T> trait.
T need to implement the SourceValue trait. This library, however, comes with implementations for all primitive numeric types.
The following code shows how this library implements SummedAreaTableSource<T> for the nalgebra::DMat<T> type.
impl <T: SourceValue>SummedAreaTableSource<T> for DMat<T>{
fn at(&self, x: usize, y: usize) -> &T {
&self[(y,x)]
}
fn height(&self) -> usize {
self.nrows()
}
fn width(&self) -> usize {
self.ncols()
}
}
