Learn R

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.