# Fortran動態陣列

`real, dimension (:,:), allocatable :: darray    `

`allocate ( darray(s1,s2) )      `

`deallocate (darray)  `

```program dynamic_array
implicit none

!rank is 2, but size not known
real, dimension (:,:), allocatable :: darray
integer :: s1, s2
integer :: i, j

print*, "Enter the size of the array:"

! allocate memory
allocate ( darray(s1,s2) )

do i = 1, s1
do j = 1, s2
darray(i,j) = i*j
print*, "darray(",i,",",j,") = ", darray(i,j)
end do
end do

deallocate (darray)
end program dynamic_array```

```Enter the size of the array: 3,4
darray( 1 , 1 ) = 1.00000000
darray( 1 , 2 ) = 2.00000000
darray( 1 , 3 ) = 3.00000000
darray( 1 , 4 ) = 4.00000000
darray( 2 , 1 ) = 2.00000000
darray( 2 , 2 ) = 4.00000000
darray( 2 , 3 ) = 6.00000000
darray( 2 , 4 ) = 8.00000000
darray( 3 , 1 ) = 3.00000000
darray( 3 , 2 ) = 6.00000000
darray( 3 , 3 ) = 9.00000000
darray( 3 , 4 ) = 12.0000000   ```

## 使用data語句

data 語句可用於初始化多個陣列，或用於陣列部分的初始化。

data 語句的語法是：

`data variable / list / ...`

```program dataStatement
implicit none

integer :: a(5), b(3,3), c(10),i, j
data a /7,8,9,10,11/

data b(1,:) /1,1,1/
data b(2,:)/2,2,2/
data b(3,:)/3,3,3/
data (c(i),i=1,10,2) /4,5,6,7,8/
data (c(i),i=2,10,2)/5*2/

Print *, 'The A array:'
do j = 1, 5
print*, a(j)
end do

Print *, 'The B array:'
do i = lbound(b,1), ubound(b,1)
write(*,*) (b(i,j), j = lbound(b,2), ubound(b,2))
end do

Print *, 'The C array:'
do j = 1, 10
print*, c(j)
end do

end program dataStatement```

```The A array:
7
8
9
10
11
The B array:
1  1  1
2  2  2
3  3  3
The C array:
4
2
5
2
6
2
7
2
8
2```

## 使用where語句

where語句可以使用陣列中的某些元素在一個表示式，根據一些邏輯條件的結果。它允許表達的執行在一個元素上，如果給定的條件為真。

```program whereStatement
implicit none

integer :: a(3,5), i , j

do i = 1,3
do j = 1, 5
a(i,j) = j-i
end do
end do

Print *, 'The A array:'

do i = lbound(a,1), ubound(a,1)
write(*,*) (a(i,j), j = lbound(a,2), ubound(a,2))
end do

where( a<0 )
a = 1
elsewhere
a = 5
end where

Print *, 'The A array:'
do i = lbound(a,1), ubound(a,1)
write(*,*) (a(i,j), j = lbound(a,2), ubound(a,2))
end do

end program whereStatement```

```The A array:
0   1   2  3  4
-1  0   1  2  3
-2  -1  0  1  2
The A array:
5   5   5  5  5
1   5   5  5  5
1   1   5  5  5```