Basic work with an R Data Frame

data_frames.R

# creating an R data frame
sim_data = data.frame(X = rnorm(n = 10),
                      Y = rnorm(n = 10),
                      Z = rnorm(n = 10))

# select column j
sim_data[,1]

# ...or by name
sim_data['X']

# select row j
sim_data[1,]

# select data point i,j
sim_data[1,1]

# additional data
more_sim_data = data.frame(X = rnorm(n = 10),
                      Y = rnorm(n = 10),
                      Z = rnorm(n = 10))

# add more rows
sim_data = rbind(sim_data, more_sim_data)

# apply a function over each column
apply(sim_data, 2, function(x) mean(x))