Getting started with R

I hope you install the R and Rstudio successfully in your PC. Data manipulation in R is different from contemporary softwares for statistical – graphical analysis. Be in mind that R is not a software, rather it is a numerical computation program like MatLab or Octave. A detailed review on the capabilities of  R were explained the post. Here we are going to start with basic data manipulation on R for extreme beginners. Let’s start with 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)

image.png

Browsing through columns 

1) Dollar method

Browse through your columns by adding $ symbol

car$

image.png

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 is

data[rows,columns]

so here it is

car[,]

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.

image.pngimage.png

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)]

image.png

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 type

car[3,3] # 3rd row and 3rd column

check the output

[1] 108

Rpointdata.jpg

Suppose you could change the value from 108 to 50

car[3,3]<- 50

Rpointdata.jpg

Change row names and column names

Row names can be changed by function rownames(), lets the check the subset data “carpart” with rownames.

image.png

check result

rownames(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

image.png

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.

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