Sampling from a dataset

In addition to generating random samples with the sample function or from any underlying probability distribution, one can sample the subset of a given dataset. In this recipe, we will introduce how to sample a subset from a financial dataset.

Getting ready

In this recipe, you need to prepare your environment with R installed and a computer that can access the Internet.

How to do it…

Please perform the following steps to sample a subset from a given financial dataset:

1. First, install and load the quantmod package:

   > install.packages("quantmod")
   > library(quantmod)
   

2. Next, we can use getSymbols to obtain the Dow Jones Industrial Average data, and then subset the 2014 data from the population:

   > getSymbols('^DJI')
   > stock = DJI['2014']
   

3. You can then randomly choose 100 samples from the dataset:

   > set.seed(5)
   > sub <- stock[sample(nrow(stock), 100), ]
   

4. Furthermore, you can calculate the daily change from the generated subset:

   > sub$change =  (sub$DJI.Close...