rbind() function combines vector, matrix or data frame by rows.

rbind(x1, x2, ..., deparse.level = 1)

x1,x2, ... : vector, matrix, data frames
deparse.level: for non matrix, 0 constructs no labels, 1 or 2 constructs labels from the argument names

data1.csv:
Subtype Gender Expression A m -0.54 A f -0.8 B f -1.03 C m -0.41

data2.csv:
Subtype Gender Expression D m 3.22 D f 1.02 D f 0.21 D m -0.04 D m 2.11 B m -1.21 A f -0.2

Read in the data from the file:

>x <- read.csv("data1.csv",header=T,sep=",")
>x2 <- read.csv("data2.csv",header=T,sep=",")

>x3 <- rbind(x,x2)
>x3

Subtype Gender Expression
1 A m -0.54
2 A f -0.80
3 B f -1.03
4 C m -0.41
5 D m 3.22
6 D f 1.02
7 D f 0.21
8 D m -0.04
9 D m 2.11
10 B m -1.21
11 A f -0.20

The column numbers of the two datasets must be the same, otherwise the combination will be meaningless.

> x <- 1:5
> x
[1] 1 2 3 4 5
> y <- 9
> rbind(x,y)
  [,1] [,2] [,3] [,4] [,5]
x    1    2    3    4    5
y    9    9    9    9    9

The row names of the result can be determined by deparse.level value. The default value of deparse.level is 1:

> rbind(x,y,3,z=12)
  [,1] [,2] [,3] [,4] [,5]
x    1    2    3    4    5
y    9    9    9    9    9
3    3    3    3    3
z   12   12   12   12   12
> rbind(x,y,3,z=12,deparse.level=0)
  [,1] [,2] [,3] [,4] [,5]
1    2    3    4    5
9    9    9    9    9
3    3    3    3    3
z   12   12   12   12   12
> rbind(x,y,3,z=12,deparse.level=2)
  [,1] [,2] [,3] [,4] [,5]
x    1    2    3    4    5
y    9    9    9    9    9
3    3    3    3    3    3
z   12   12   12   12   12