R(9), Data Reshaping
Data Reshaping in R is about changing how data is organized into rows and columns. Most of the time data processing in R is done by using input data as data frames. It is easy to extract data from the rows and columns of a data frame, but in some cases, the type of the data frame that we need is different from the one we received.
Add rows and columns into a data frame
We can use cbind() to connect multiple vectors to create a data frame. Also, we can use rbind() to merge two data frames.
cbind: column bind
rbind: row bind
# Create vector objects.
city <- c("Tampa","Seattle","Hartford","Denver")
state <- c("FL","WA","CT","CO")
zipcode <- c(33602,98104,06161,80294)
# Combine above three vectors into one data frame.
addresses <- cbind(city,state,zipcode)
# Print a header.
cat("# # # # The First data frame
")
# Print the data frame.
print(addresses)
# Create another data frame with similar columns
new.address <- data.frame(
city = c("Lowry","Charlotte"),
state = c("CO","FL"),
zipcode = c("80230","33949"),
stringsAsFactors = FALSE
)
# Print a header.
cat("# # # The Second data frame
")
# Print the data frame.
print(new.address)
# Combine rows form both the data frames.
all.addresses <- rbind(addresses,new.address)
# Print a header.
cat("# # # The combined data frame
")
# Print the result.
print(all.addresses)
results:
# # # # The First data frame
city state zipcode
[1,] "Tampa" "FL" "33602"
[2,] "Seattle" "WA" "98104"
[3,] "Hartford" "CT" "6161"
[4,] "Denver" "CO" "80294"
# # # The Second data frame
city state zipcode
1 Lowry CO 80230
2 Charlotte FL 33949
# # # The combined data frame
city state zipcode
1 Tampa FL 33602
2 Seattle WA 98104
3 Hartford CT 6161
4 Denver CO 80294
5 Lowry CO 80230
6 Charlotte FL 33949
Merge Data Frames
If we use merge() to merge two data frames, the column name of the data frames must be the same.
Data Reshaping is a little hard to understand, understand and master it in latter practice.