str(df) #shows the internal structure of the data frame
head(df) # tells you the first six lines of a vector, matrix, table, data frame, or function
tail(df) # tells you the last six lines of a vector, matrix, table, data frame, or function
summary(df) # shows the statistical summary
ls() # lists all of the objects available in the workspace, i.e., all the data and variables you have defined
ls.str() # combines ls and str to lists all objects with details about data type and content
class() # tells you the data type, i.e., vector, matrix, character, etc.
names() # can either change the name of an object or tells you all of the defined names in the object
object.size() # tells you how much memory is taken up on your computer by the object
dim() # tells you the dimensions of the object
length() # tells you the length (number) of the vectors and factors in the object
ncol() # tells you the number of columns
nrow() # tells you the number of rows
Let’s say we want to find the mean of the input column “TOTINC” in R. We do that as shown below:
Hence, to access TOTINC, we need to use df$TOTINC. However, to access the columns directly in R, you can use the function attach, after which you can refer to the columns directly as shown below:
You can and should use detach(df) to detach the data frame once you don’t need to directly access the variables.
Note: When working with multiple data frames, DO NOT use attach as it might cause a lot of confusion, rather use WITH() function, the details of which are beyond the scope of this document.