I am attempting to eval a new field, from two other fields:     | eval 4XXError=if(metric_name="4XXError", statistic_value, null()) | eval 5XXError=if(metric_name="5XXError", statistic_value, null()) | eval total_errors='4XXError'+'5XXError'       when I come to stat them out:     | stats last(4XXError), last(5XXError), last(total_errors) by api_name, http_method, url       the total_errors column is just blank:   where am i going wrong?    also why does 4XXError need to be single-quoted? is it because it starts with a number?   ... View more