logical. Should missing values (including NaN) be removed?
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Value
Pinna Combinative index
Formula
$$PICI = \frac {1}{2} \left(\frac{P}{TG+10}+\frac{12Pdm}{TGdm+10}\right)$$ P = annual precipitation (mm); TG = annual mean temperature (Celsius); Pdm= precipitation of the driest month; TGdm= temperature of the driest month
References
Zambakas J. 1992. General Climatology. Department of Geology, National & Kapodistrian University of Athens: Athens, Greece.