SUMMARY ------ I am trying to program in PostgreSQL a statistics function.
My old method in SQL is here. select ( avg(measure) - 0.0 ) / nullif(stddev_pop(case when measure > 0.00 then 0.00 else measure end ),0) sortino_true from TABLE/VIEW; The logic is based on SORTINO RATIO: ARE YOU CALCULATING IT WRONG? SEPTEMBER 11, 2013 https://www.rcmalternatives.com/2013/09/sortino-ratio-are-you-calculating-it-wrong/ In PostgreSQL C, how do I get access to the 'X' (data) variable? DETAILS ------- I see a similar function with other variables in here. But I am not trying to re-program 'stddev_samp'. float8_stddev_samp ( lines 2741 through 2767 ) https://github.com/postgres/postgres/blob/9a34123bc315e55b33038464422ef1cd2b67dab2/src/backend/utils/adt/float.c N = transvalues[0]; sumX = transvalues[1]; sumX2 = transvalues[2]; The following article explains it and this makes sense. Sum of Squares Formula Shortcut https://www.thoughtco.com/sum-of-squares-formula-shortcut-3126266 I can match article symbols to PostgreSQL C varaibles. numerator = N * sumX2 - sumX * sumX; N * SIGMA(X**2) - (SIGMA(X))**2 BUT I NEED ... -------------- However in my case, I have this adjustement "case when measure > 0.00 then 0.00 else measure end" So the case seems that I need access to 'X' but access to sumX and sumX2 are only shown. How would I get accress to X? May anyone point me to a simple good working example? Thanks, Andre Mikulec andre_miku...@hotmail.com