Function interp_abline 

fn interp_abline(
    _args: &[RValue],
    named: &[(String, RValue)],
    context: &BuiltinContext<'_>,
) -> Result<RValue, RError>

Add horizontal, vertical, or slope-intercept lines to the current plot.

@param a intercept (for slope-intercept form) @param b slope (for slope-intercept form) @param h y-value for horizontal line @param v x-value for vertical line @param col color @param lwd line width @return NULL (invisibly)