Indirect gradient analysis - Alaska Geobotany Center

Calculation of x values along the 1st axis
A and B are the plots at the
ends of the first axis.
P is the plot to position with
reference to the A and B.
P has dissimilarity of dA with
reference to Plot A and
dissimilarity dB with respect
to Plot B.
Solving for x:
x 2 + e 2 = (dA) 2 , e 2 = (dA) 2 - x 2
(L-x) 2 + e 2 = (dB) 2
(L-x) 2 + (dA) 2 - x 2 = (dB) 2
L 2 - 2Lx + x 2 + (dA) 2 - x 2 = (dB) 2
L 2 - 2Lx + (dA) 2 = (dB) 2
x =( L 2 + (dA) 2 - (dB) 2 )/2L
Using a compass, P can be
positioned with respect to A
and B.
The perpendicular from P to
the first axis is e.
x is the distance of P from A
and is calculated by the
Pythagorean theorem.