I'm trying to change a data frame variable to a factor variable but having issues

Question

> summary(CA_extract[2])
 REPORTING_YEAR
 Min.   :1990  
 1st Qu.:1995  
 Median :2010  
 Mean   :2007  
 3rd Qu.:2017  
 Max.   :2019  
> table(CA_extract[2])