Creating tables with big.matrix objects
A final advantage to using big.matrix is that if you know how to use R's matrices, then you know how to use a big.matrix. You can subset columns and rows just as you would a regular matrix, using a numeric or character vector and the object returned is an R matrix. Likewise, assignments are the same as with R matrices and after those assignments are made they are stored on disk and can be used in the current and future R sessions.
One thing to remember is that $ is not valid for getting a column of either a matrix or a big.matrix.
Questo esercizio fa parte del corso
Scalable Data Processing in R
Istruzioni dell'esercizio
- Create a new variable
mortby attaching the"mortgage-sample.desc"file. - Look at the first 3 rows of
mort. - Create a table of the number of mortgages for each year in the data set. The column name in the data set is
"year".
Esercizio pratico interattivo
Prova a risolvere questo esercizio completando il codice di esempio.
# Create mort
mort <- ___
# Look at the first 3 rows
mort[___, ]
# Create a table of the number of mortgages for each year in the data set
table(___)