merge                  package:base                  R Documentation

_M_e_r_g_e _T_w_o _D_a_t_a _F_r_a_m_e_s

_D_e_s_c_r_i_p_t_i_o_n:

     Merge two data frames by common columns or row names.

_U_s_a_g_e:

     merge(x, y, by, by.x, by.y, sort = TRUE)

_A_r_g_u_m_e_n_t_s:

    x, y: data frames, or objects to be coerced to one

by, by.x, by.y: specifcations of the common columns. See Details.

    sort: logical. Should the results be sorted on the `by' columns?

_D_e_t_a_i_l_s:

     By default the data frames are merged on the columns with names
     they both have, but separate specifcations of the columns can be
     given by `by.x' and `by.y'. Columns can be specified by name,
     number or by a logical vector: the name `"row.names"' or the
     number `0' specifies the row names.  The rows in the two data
     frames that match on the specified columns are extracted, and
     joined together. If there is more than one match, all possible
     matches contribute one row each.

     If the remaining columns in the data frames have any common names,
     these have `".x"' and `".y"' appended to make the names of the
     result unique.

_V_a_l_u_e:

     A data frame. The rows are by default lexicographically sorted on
     the common columns, but are otherwise in the order in which they
     occurred in `x'. The columns are the common columns followed by
     the remaining columns in `x' and then those in `y'.  If the
     matching involved row names, an extra column `Row.names' is added
     at the left, and in all cases the result has no special row names.

_S_e_e _A_l_s_o:

     `data.frame', `by', `cbind'

_E_x_a_m_p_l_e_s:

     authors <- data.frame(
         surname = c("Tukey", "Venables", "Tierney", "Ripley", "McNeil"),
         nationality = c("US", "Australia", "US", "UK", "Australia"),
         retired = c("yes", rep("no", 4)))
     books <- data.frame(
         name = c("Tukey", "Venables", "Tierney", "Ripley", "Ripley", "McNeil"),
         title = c("Exploratory Data Analysis",
                   "Modern Applied Statistics ...",
                   "LISP-STAT",
                   "Spatial Statistics", "Stochastic Simulation",
                    "Interactive Data Analysis"),
         other.author = c(NA, "Ripley", NA, NA, NA, NA))

     merge(authors, books, by.x="surname", by.y="name")
     merge(books, authors, by.x="name", by.y="surname")

