Data Structures Summary

Vector

  • A vector in R can contain any number of elements, but all of the elements must be of the same type – that is a vector cannot contain a mix of numbers, logical, and character types.
  • The c() function is used for creating the Vector.
  • Factor

  • The factor() function is used for encoding a vector as a factor. A factor() function is a special case of vector that is used for representing nominal or categorical or ordinal data.
  • List

  • A list is used for storing an ordered set of elements. While a vector requires all its elements to be of the same type, a list allows different types of elements.
  • The list() function is used for creating the list.
  • Matrix

  • A matrix is a two-dimensional table with rows and columns of data. Like vectors, R matrices can contain one type of data and are typically used for only storing numeric data.
  • The matrix() function is used for creating a matrix.
  • The function cbind() can be used for constructing a matrix using vectors.
  • Data Frame

  • The data.frame() function is used for constructing the data frame.
  • The cbind() function is used for adding a column into the data frame. A column into the data frame can be added using a new column name in the format – frame$column-name.
  • The rbind() function is used for adding a row into the data frame. A new row can be added using nrow() function.
  • The merge() function is used for merging two data frames.
  • Number of rows and columns in the data frame can be found by nrow(), ncol(), and dim() functions.
  • Row and Columns names can be found by nrownames(), ncolnames(), and dimnames() functions.