Example 3-2 selects rows from an ordered ore.frame object. The example first adds a column to the iris data.frame object for use in creating an ordered ore.frame object. It invokes the ore.drop function to delete the database table IRIS_TABLE, if it exists. It then creates a database table, with the corresponding proxy ore.frame object IRIS_TABLE, from the iris data.frame. The example invokes the ore.exec function to execute a SQL statement that makes the RID column the primary key of the database table. It then invokes the ore.sync function to synchronize the IRIS_TABLE ore.frame object with the table and displays the first three rows of the proxy ore.frame object.
Example 3-2 next selects 51 rows from IRIS_TABLE by row number and creates the ordered ore.frame object iris_selrows with them. It displays the first six rows of iris_selrows. It then selects 3 rows by row name and displays the result.
Example 3-2 Selecting Data by Row
# Add a column to the iris data set to use as row identifiers.
iris$RID <- as.integer(1:nrow(iris) + 100)
ore.drop(table = 'IRIS_TABLE')
ore.create(iris, table = 'IRIS_TABLE')
ore.exec("alter table IRIS_TABLE add constraint IRIS_TABLE
primary key (\"RID\")")
ore.sync(table = "IRIS_TABLE")
head(IRIS_TABLE, 3)
# Select rows by row number.
iris_selrows <- IRIS_TABLE[50:100,]
head(iris_selrows)
# Select rows by row name.
IRIS_TABLE[c("101", "151", "201"),]
Listing for Example 3-2
R> # Add a column to the iris data set to use as row identifiers.
R> iris$RID <- as.integer(1:nrow(iris) + 100)
R> ore.drop(table = 'IRIS_TABLE')
R> ore.create(iris, table = 'IRIS_TABLE')
R> ore.exec("alter table IRIS_TABLE add constraint IRIS_TABLE
+ primary key (\"RID\")")
R> ore.sync(table = "IRIS_TABLE")
R> head(IRIS_TABLE, 3)
Sepal.Length Sepal.Width Petal.Length Petal.Width Species RID
101 5.1 3.5 1.4 0.2 setosa 101
102 4.9 3.0 1.4 0.2 setosa 102
103 4.7 3.2 1.3 0.2 setosa 103
R> # Select rows by row number.
R> iris_selrows <- IRIS_TABLE[50:100,]
R> head(iris_selrows)
Sepal.Length Sepal.Width Petal.Length Petal.Width Species RID
150 5.0 3.3 1.4 0.2 setosa 150
151 7.0 3.2 4.7 1.4 versicolor 151
152 6.4 3.2 4.5 1.5 versicolor 152
153 6.9 3.1 4.9 1.5 versicolor 153
154 5.5 2.3 4.0 1.3 versicolor 154
155 6.5 2.8 4.6 1.5 versicolor 155
R> # Select rows by row name.
R> IRIS_TABLE[c("101", "151", "201"),]
Sepal.Length Sepal.Width Petal.Length Petal.Width Species RID
101 5.1 3.5 1.4 0.2 setosa 101
151 7.0 3.2 4.7 1.4 versicolor 151
201 6.3 3.3 6.0 2.5 virginica 201