# Simple helper just for this example
proc map {n exp list} {
    upvar 1 $n v
    set r {}; foreach v $list {lappend r [uplevel 1 $exp]}; return $r
}

# Data from wikipedia
set x {
    1.47 1.50 1.52 1.55 1.57 1.60 1.63 1.65 1.68 1.70 1.73 1.75 1.78 1.80 1.83
}
set y {
    52.21 53.12 54.48 55.84 57.20 58.57 59.93 61.29 63.11 64.47 66.28 68.10
    69.92 72.19 74.46
}
# Wikipedia states that fitting up to the square of x[i] is worth it
puts [regressionCoefficients $y [map n {map v {expr {$v**$n}} $x} {0 1 2}]]