Here I have to do mapping of missions of an program to the PEOs( program educational objectives) of that program...So I have made a table and divided it into rows and columns..Now I give the weightage values as 1(low), 2(medium),3(high) and blank as drop down...If missions are correlated with the PEO's then they will select any of the value from the drop down and if not correlate then will select the blank...So my question is after selecting the values from drop down I have to calculate the average of each of the PEOs. How can I calculate the average from the table ignoring the null values and how can I submit the average values and store it to database...Give me some ideas...This have to be done by php, JavaScript coding...