Function flot::valr

pub fn valr<'a, I, T>(y: I) -> Box<Iterator<Item = (f64, f64)> + 'a> where
    I: IntoIterator<Item = &'a T> + 'a,
    T: Into<f64> + Copy + 'a, 

data from an iterator of references plotted against index. Like zip, the reference type can be anything that converts to f64