Second-order bivariate differentiation calculation.
SecondOrderMixedDiffVal(value.c, value.x.p, value.x.m, value.y.p,
value.y.m, value.xy.p, value.xy.m, epsilon)
function value at (x,y)
.
function value at (x+epsilonx,y)
.
function value at (x-epsilon,y)
.
function value at (x,y+epsilon)
.
function value at (x,y-epsilon)
.
function value at (x+epsilon,y+epsilon)
.
function value at (x-epsilon,y-epsilon)
.
offset value for both x
and y
.
(value.p -2*value.c + value.m) / (2*epsilon)
.