Inequality in a_j == a_c calculation when iabs == 0

[davidorme]

Hi,

Connected to #11, one way you get a mismatch between a_j and a_c is when iabs is zero.

a_j

fact_jmaxlim <- vcmax * (ci + 2 * gammastar)/(kphio * iabs * (ci + kmm))
a_j <- kphio * iabs * (ci - gammastar)/(ci + 2 * gammastar) * fact_jmaxlim

Because fact_jmaxlim has vcmax in the numerator and iabs in the denominator, this gives 0/0 and hence both it and a_j are NaN when iabs is zero.

a_c

In contrast:

a_c <- vcmax * (ci - gammastar)/(ci + kmm)

Here iabs only features in numerator via vcmax and so is 0/real = 0.

In practice, I guess the equation for a_j should be set to zero when there is no photosynthetically active light, and that needs to be trapped to allow the test in #11 to work correctly.