R

A data frame is a table

The column names should be non-empty
The row names should be unique
The data stored in a data frame can be of numeric, factor or character type
Each column should contain same number of data items

emp.data <- data.frame(
   emp_id = c (1:5), 
   emp_name = c("Rick","Dan","Michelle","Ryan","Gary"),
   salary = c(623.3,515.2,611.0,729.0,843.25), 
   
   start_date = as.Date(c("2012-01-01", "2013-09-23", "2014-11-15", "2014-05-11",
      "2015-03-27")),
   stringsAsFactors = FALSE
)

print(emp.data)
str(emp.data) # structure
print(summary(emp.data)) # summary

emp.data <- data.frame(
   emp_id = c (1:5), 
   emp_name = c("Rick","Dan","Michelle","Ryan","Gary"),
   salary = c(623.3,515.2,611.0,729.0,843.25), 
   
   start_date = as.Date(c("2012-01-01", "2013-09-23", "2014-11-15", "2014-05-11",
      "2015-03-27")),
   stringsAsFactors = FALSE
)

print(emp.data$emp_name) # get column, vector
print(emp.data[1, ]) # get row, dataframe
print(emp.data[1, 2]) # get a specific element

emp.data <- data.frame(
   emp_id = c (1:5), 
   emp_name = c("Rick","Dan","Michelle","Ryan","Gary"),
   salary = c(623.3,515.2,611.0,729.0,843.25), 
   
   start_date = as.Date(c("2012-01-01", "2013-09-23", "2014-11-15", "2014-05-11",
      "2015-03-27")),
   stringsAsFactors = FALSE
)

print(names(emp.data)) # names
print(dim(emp.data)) # dim

emp.data$dept <- c("IT","Operations","IT","HR","Finance") # add a column
print(emp.data)

emp.data = emp.data[, names(emp.data) != "dept"] # remove a column
print(emp.data)

# add a row
new.emp.data <- data.frame(
	emp_id = 6,
	emp_name = "Mike",
	salary = 700,
	start_date = as.Date("2010-01-01"),
	stringsAsFactors = FALSE
			   )
emp.data = rbind(emp.data, new.emp.data)
print(emp.data)

# remove a row
print(emp.data[c(1:2, 4:dim(emp.data)[1]),])

# add a column
library(dplyr)
emp.data <- emp.data %>% mutate(salary_year = salary*12)
print(emp.data)

# filter
emp.data = emp.data %>% filter(salary > 700)
print(emp.data)