I usually calculate monthly or 3-monthly Standardized Precipitation Index (SPI) using spreadsheet, based on daily rainfall from weather station. Attached is the spreadsheet example link.
And now I would like to use satellite precipitation estimate (raster data) to calculate the SPI. The problem is in the spreadsheet I use some function like: FREQUENCY, GAMA.DIST, NORMSINV.
Is there any similar above function in ArcGIS Desktop?