multiple column mean

[#1]

See attached, I tried to add a new column for mean from 3 other columns by "col mean( col1, col2, col3)". But the mean seems a little bit off, and I used "(col1+col2+col3)/3" to verify, and it gives me the correct result. What is the possible cause of this? 

[#2 · Accepted solution]

You don't want the Col Mean() function, you just want the Mean() function

[#3 · Accepted solution]

Expanding on @txnelson's suggestion, the Col Mean() function uses the additional arguments after the first to group the data. This behavior is very convenient, but, as he said, not what you want this time.