The Allometric Equation

Consider two correlated trait measures: x & y
A non-linear growth relationship between them can be expressed:  y = mx^a
    To express this as proportional change, use a log scale: ln(y) = ln(m) + a ln(x)
In this form, the equation is linear and ln(m) is the y-intercept.
    If x is a general size measure, then y starts growing with x:
    since  y = 0 when x = 0, then ln(m) = 0

The Allometric Equation then simplies to  ln(y) = a ln(x),
    which can then be rewritten  Y' = a X' , where a = allometric coefficient