For Merging Data frames :

df1<-data.frame(age = c(23,13,27,36,14),name = c("Bilal","hamza","hassan","haseeb","Tooba"))

df2<-data.frame(name = c("talha","manan","Abdullah","shayan","hanan"),gpa = c(2.1,1.3,2.5,2.6,3.6))

df3<-data.frame(age = c(21,13,25,26,23),name = c("saad","Adeel","Waleed","ubaid","Irum"))

ndf1<-merge(df1,df3, all = TRUE)
merge(df1,df2, all = TRUE)
##        name age gpa
## 1  Abdullah  NA 2.5
## 2     Bilal  23  NA
## 3     hamza  13  NA
## 4     hanan  NA 3.6
## 5    haseeb  36  NA
## 6    hassan  27  NA
## 7     manan  NA 1.3
## 8    shayan  NA 2.6
## 9     talha  NA 2.1
## 10    Tooba  14  NA
merge(df2,df3, all = TRUE)
##        name gpa age
## 1  Abdullah 2.5  NA
## 2     Adeel  NA  13
## 3     hanan 3.6  NA
## 4      Irum  NA  23
## 5     manan 1.3  NA
## 6      saad  NA  21
## 7    shayan 2.6  NA
## 8     talha 2.1  NA
## 9     ubaid  NA  26
## 10   Waleed  NA  25
ndf1
##    age   name
## 1   13  Adeel
## 2   13  hamza
## 3   14  Tooba
## 4   21   saad
## 5   23  Bilal
## 6   23   Irum
## 7   25 Waleed
## 8   26  ubaid
## 9   27 hassan
## 10  36 haseeb
rbind function
x<-1:4
y<-5:8
z<-9:12
rbind(x,y)
##   [,1] [,2] [,3] [,4]
## x    1    2    3    4
## y    5    6    7    8
cbind function
cbind(x,y,z)
##      x y  z
## [1,] 1 5  9
## [2,] 2 6 10
## [3,] 3 7 11
## [4,] 4 8 12

Merging two data frames

df1 <- data.frame(Id = c(333, 444, 555, 777, 999),
                 Product = c("laptop", "printer", "tablet", "desk", "chair")
                 )

df2 <- data.frame(Id = c(333, 444, 666, 777, 888),
                 Price = c(1200, 150, 300, 450, 200)
                 )

merge(df1, df2, by = "Id")
##    Id Product Price
## 1 333  laptop  1200
## 2 444 printer   150
## 3 777    desk   450
df1<-data.frame(age = c(23,13,27,36,14),name = c("Bilal","hamza","hassan","haseeb","Tooba"))

df2<-data.frame(name = c("talha","manan","Abdullah","shayan","hanan"),gpa = c(2.1,1.3,2.5,2.6,3.6))

df3<-data.frame(age = c(21,16,25,26,23),name = c("saad","Adeel","Waleed","ubaid","Irum"))

new_1<-ndf1$age>=20
new_1<-ndf1$name[new_1]
new_1
## [1] "saad"   "Bilal"  "Irum"   "Waleed" "ubaid"  "hassan" "haseeb"