How to use the where clause in R programming

Question

I'm trying to implement a where clause within ggplot. Is this possible? 

My problem statement is that, I'm using the diamonds table and I want to select records where the cut = "Good". Cut is a field in the Diamond table. The Cut field can equal "Fair", "Good", Very Good", "Premium", and "Ideal".

diamonds[1:5,]
#   carat     cut   color  clarity    depth  table   price         x    y    z
# 1  0.23   Ideal       E      SI2     61.5     55     326      3.95 3.98 2.43  

I want to use some type of conditional statement against a CSV read file. But to keep my example simple, I using the diamond table as a typical example of my problem. I want to filter cut = "Good" but to include fields related to the records = "Good".

Any help would be appreciated.