Parallel Computing for Data Science

298 APPENDIX B. R QUICK START

us e r system e l a ps e d

0. 0 0 8 0 .00 0 0 . 006

> system . time ({s <− 0 ;

for ( i i n 1:10 0 0 000 ) s <− s + x [ i ] })

us e r system e l a ps e d

2. 7 7 6 0 .00 4 2 . 859

B.4 Second Sample Programming Session

A matrix is a special case of a vector, with added class attributes, the

numbers of rows and columns.

# rowbind () fu n c t i o n combines rows o f m a tri c e s ;

# there ’ s a cbind () f o r columns too

> m1 <− rbind ( 1 : 2 , c ( 5 , 8 ) )

> m1

[ , 1 ] [ , 2 ]

[ 1 , ] 1 2

[ 2 , ] 5 8

> rbind (m1, c (6 , −1))

[ , 1 ] [ , 2 ]

[ 1 , ] 1 2

[ 2 , ] 5 8

[ 3 , ] 6 −1

# form matri x from 1 ,2 ,3 ,4 ,5 , 6 , in 2 rows ;

# R u