recalculate outcome since start GRIIS (1700)

[jrhillae]

@mtrekels : when comparing the outcome for 1970 up to now, or 1700 up to now for Flanders there is a large difference.

I have the following questions:

• What is the unit of effective rate in these files? Number of new species per year? I think so as we agreed to report this, but I can not see a trace for the unit defind in your code.

• Years are missing in the dataset between 1700 and 2025. Only 153 datarows are available. Does this affect the calculation?

• Do you think if the calculation is correct that it is normal or expected that the value is lower when calculating for a longer timeperiod?

• I think it is strange that the effective rate is constant over time since 1700. This gives me the impression that something is not going the way as expected. We should expect it increases over time right since 1700 and it seems to be constant (about 9 per year)?

[jrhillae]

@mtrekels : de uitkomst nu klopt niet (9.03 nieuwe soorten per jaar sinds 1700):

de eerste grafiek die uit de analyse komt (hieronder) klopt wel dus ergens in de code erna zou er een bug zitten.