1 of 1 people found this helpful
If this is exactly what your data looks like then :
[Error] / [Success]
would work on a row basis. Format it as a percent instead of multiplying it by 100.
However, the better equation is:
sum([Error)] /sum( [Success])
As it will work on the row and roll up (If you want to aggregate rows - e.g. all servers at a location)
Here's a great blog post on aggregate vs. row level calcs: http://www.theinformationlab.co.uk/2012/03/27/tableau-for-excel-users-part-2-calculated-fields/
If your data does not look like this, then a sample workbook (tbwx) would be useful.