Function flot::mapr

pub fn mapr<'a, I, T, F>(x: I, f: F) -> Box<Iterator<Item = (f64, f64)> + 'a> where
    I: IntoIterator<Item = &'a T> + 'a,
    F: Fn(f64) -> f64 + 'a,
    T: Into<f64> + Copy + 'a, 

map an iterator of references with a function producing point tuples. Like zip, the reference type can be anything that converts to f64