data( mtcars), which is usually an inbuilt dataset. To make you know how to import a data from your PC, just go to the link here.car<- mtcars
View(mtcars)
Browsing through columns
1) Dollar method
Browse through your columns by adding $ symbolcar$
2) Square bracket and number/name method
Other methods are by using [] square brackets, or by using the exact column names(if you know) or by tab <=> button. However the result will be the same. Like maths, in R you can solve the same problems in different ways. Use the codes according to your convenience, and your data structure. Inside the [] , the data is represented by rows and columns.The basic structure isdata[rows,columns]
so here it iscar[,]
You could select desired columns by using "tab" button, when the cursor is in the square bracket[ ]. Similarly, you can shift the cursor left to the coma for rows.
you can use numbers instead of names of columns. i e, for the first column use 1 and for the second column use 2.car[,1] # For first column
car[2,]# For second column
Get first four columns from the data[car], you have to select multiple columns by using the command "c".car[,c(1,2,3,4)] # first four columns by using no.s.
car[,c("mpg","cyl","disp","hp")] #first four columns by using names.
In the same way you can use rows too. Lets check the first 4 rows.car[c(1,2,3,4),] # first four rows by number
car[c("Mazda RX4","Mazda RX4 Wag","Datsun 710","Hornet 4 Drive"),]#first four rows by name
Everything in the R needs a name, as in real life scenario. Otherwise R will forgot, and won't seen on global environment. carpart<- car[,c(1,2,3,4)]
This way you can define the subsets, i e you made your own dataset from the previous one.
Point data manipulation
You can do point data editing in R, before you doing this you should have a better understanding on datasets you are dealing with. For this you have to specify both rows and columns.
just typecar[3,3] # 3rd row and 3rd column
check the output[1] 108
Suppose you could change the value from 108 to 50car[3,3]<- 50
Change row names and column names
Row names can be changed by function rownames(), lets the check the subset data "carpart" with rownames.
check resultrownames(carpart)
[1] "Mazda RX4" "Mazda RX4 Wag" "Datsun 710" "Hornet 4 Drive" "Hornet Sportabout"
[6] "Valiant" "Duster 360" "Merc 240D" "Merc 230" "Merc 280"
[11] "Merc 280C" "Merc 450SE" "Merc 450SL" "Merc 450SLC" "Cadillac Fleetwood"
[16] "Lincoln Continental" "Chrysler Imperial" "Fiat 128" "Honda Civic" "Toyota Corolla"
[21] "Toyota Corona" "Dodge Challenger" "AMC Javelin" "Camaro Z28" "Pontiac Firebird"
[26] "Fiat X1-9" "Porsche 914-2" "Lotus Europa" "Ford Pantera L" "Ferrari Dino"
[31] "Maserati Bora" "Volvo 142E"
If you want to know column names, you can use two commands> colnames(carpart) # colnames is a specific function
[1] "mpg" "cyl" "disp" "hp"
> names(carpart)# names only work work for dataframes
[1] "mpg" "cyl" "disp" "hp"
You can change the column names/row names by assign the new names in order, lets check the column names. > names(carpart)
[1] "mpg" "cyl" "disp" "hp"
Now assign with new name.names(carpart)<- c("miles/gal","cylinder","displacement","horsepower")
# or
colnames(carpart)<- c("miles/gal","cylinder","displacement","horsepower")
let's check the new column names
I hope this will you make you start the R program from scratch, More advanced topics are coming soon. Please follow the category R-spells.
