Matrix 如何求矩阵的维数？
我有一个包含字符和实数的矩阵，我想要一个程序来读取这个矩阵（自己查找维度）。这是我的密码：Matrix 如何求矩阵的维数？,matrix,fortran,dimension,Matrix,Fortran,Dimension,我有一个包含字符和实数的矩阵，我想要一个程序来读取这个矩阵（自己查找维度）。这是我的密码： ! A fortran95 program for G95 Program Project2nd implicit none character(len=40), allocatable :: a(:,:) integer i,j,k,n,m,l,st character(len=40) d n=0; m=1; j=1; open(10,file=& '/Users/dariakowsari/
! A fortran95 program for G95
Program Project2nd
implicit none
character(len=40), allocatable :: a(:,:)
integer i,j,k,n,m,l,st
character(len=40) d
n=0; m=1; j=1;
open(10,file=&
'/Users/dariakowsari/Documents/Physics/Programming/Fortran95-Projects/Project2nd/input.txt', &
IOstat=st)
do while (st == 0)
read(10,*,IOstat=st) d
n=n+1
end do
st=0
do j=1,m
do while (st == 0)
allocate(a(1,m))
read(10,*,IOstat=st) (a(1,j),j=1,m)
m=m+1
deallocate(a)
end do
print*, n,m
end
a b 13 15.5 13.2
c d 16 16.75 19
e f 19.2 12.2 18.2
通过这段代码，我得到了矩阵维数的（3,2）。您的示例代码中有一些错误，这意味着它不能为我编译，但经过一些更改后，我设法得到了与您类似的结果。 *更新：正如@francescalus在对我的另一个（现已删除）答案的评论中所指出的，这种方法涉及未定义的行为，因此不是一个合适的解决方案。这是因为试图从文件中读取的元素比当前的多。） 这里有一种替代方法，可以避免这种未定义的行为，但可能效率很低
Program Project2nd
implicit none
character(len=40), allocatable :: a(:)
integer, allocatable :: ind(:)
integer, parameter :: maxElements = 100
integer i,j,n,m,st
character(len=40) d
n=0;
open(10,file='mat.txt',IOstat=st)
!Find number of lines
do while (st == 0)
read(10,*,IOstat=st) d
if(st ==0) n=n+1
end do
!Move back to the start of the file
rewind(10)
!Read all of the data
do m=n,maxElements,n
allocate(a(m))
read(10,*,IOstat=st) a
deallocate(a)
rewind(10)
if(st.ne.0) exit
enddo
m = m -n !Need to roll back m by one iteration to get the last which worked.
if(mod(m,n).ne.0) then
print*,"Error: Number of elements not divisible by number of rows."
stop
endif
!Number of columns = n_elements/nrow
m=m/n
print*, n,m
end Program Project2nd
maxElementdo st = 0 ; m = n
do while (st==0)
allocate(a(m))
read(10,*,IOstat=st) a
deallocate(a)
rewind(10)
if(st.ne.0) then
m = m - n !Go back to value of m that worked
exit
endif
m=m+n
enddo
您的示例代码中有一些错误，这意味着它不能为我编译，但经过一些更改后，我设法得到了与您类似的结果。 *更新：正如@francescalus在对我的另一个（现已删除）答案的评论中所指出的，这种方法涉及未定义的行为，因此不是一个合适的解决方案。这是因为试图从文件中读取的元素比当前的多。） 这里有一种替代方法，可以避免这种未定义的行为，但可能效率很低
Program Project2nd
implicit none
character(len=40), allocatable :: a(:)
integer, allocatable :: ind(:)
integer, parameter :: maxElements = 100
integer i,j,n,m,st
character(len=40) d
n=0;
open(10,file='mat.txt',IOstat=st)
!Find number of lines
do while (st == 0)
read(10,*,IOstat=st) d
if(st ==0) n=n+1
end do
!Move back to the start of the file
rewind(10)
!Read all of the data
do m=n,maxElements,n
allocate(a(m))
read(10,*,IOstat=st) a
deallocate(a)
rewind(10)
if(st.ne.0) exit
enddo
m = m -n !Need to roll back m by one iteration to get the last which worked.
if(mod(m,n).ne.0) then
print*,"Error: Number of elements not divisible by number of rows."
stop
endif
!Number of columns = n_elements/nrow
m=m/n
print*, n,m
end Program Project2nd
maxElementdo st = 0 ; m = n
do while (st==0)
allocate(a(m))
read(10,*,IOstat=st) a
deallocate(a)
rewind(10)
if(st.ne.0) then
m = m - n !Go back to value of m that worked
exit
endif
m=m+n
enddo
下面是如何进行w/o倒带
implicit none
character(len=100) wholeline
character(len=20), allocatable :: c(:)
integer iline,io,ni,nums
open(20,file='testin.dat')
iline=0
do while(.true.)
read(20,'(a)',iostat=io)wholeline
if(io.ne.0)exit
iline=iline+1
ni=lineitems(wholeline)
allocate(c(ni))
read(wholeline,*)c
nums=ctnums(c)
write(*,*)'line',iline,' contains ',ni,'items',nums,
$ 'are numbers'
deallocate(c)
enddo
write(*,*)'total lines is ',iline
contains
integer function ctnums(c)
! count the number of items in a character array that are numbers
! this is a template,
! obviously you could assign the numbers to a real array here
character(len=*), allocatable :: c(:)
real f
integer i,io
ctnums=0
do i = 1,size(c)
read(c(i),*,iostat=io)f
if(io.eq.0)ctnums=ctnums+1
enddo
end function
integer function lineitems(line)
! count the number of items in a space delimited string
integer,parameter ::maxitems=100
character(len=*) line
character(len=80) :: c(maxitems)
integer iline,io
lineitems=0
do iline=1,maxitems
read(line,*,iostat=io)c(:iline)
if(io.ne.0)return
lineitems=iline
enddo
if(lineitems.eq.maxitems)write(*,*)'warning maxitems reached'
end function
end
line 1 contains 5 items 3 are numbers
line 2 contains 5 items 3 are numbers
total lines is 2
下面是如何进行w/o倒带
implicit none
character(len=100) wholeline
character(len=20), allocatable :: c(:)
integer iline,io,ni,nums
open(20,file='testin.dat')
iline=0
do while(.true.)
read(20,'(a)',iostat=io)wholeline
if(io.ne.0)exit
iline=iline+1
ni=lineitems(wholeline)
allocate(c(ni))
read(wholeline,*)c
nums=ctnums(c)
write(*,*)'line',iline,' contains ',ni,'items',nums,
$ 'are numbers'
deallocate(c)
enddo
write(*,*)'total lines is ',iline
contains
integer function ctnums(c)
! count the number of items in a character array that are numbers
! this is a template,
! obviously you could assign the numbers to a real array here
character(len=*), allocatable :: c(:)
real f
integer i,io
ctnums=0
do i = 1,size(c)
read(c(i),*,iostat=io)f
if(io.eq.0)ctnums=ctnums+1
enddo
end function
integer function lineitems(line)
! count the number of items in a space delimited string
integer,parameter ::maxitems=100
character(len=*) line
character(len=80) :: c(maxitems)
integer iline,io
lineitems=0
do iline=1,maxitems
read(line,*,iostat=io)c(:iline)
if(io.ne.0)return
lineitems=iline
enddo
if(lineitems.eq.maxitems)write(*,*)'warning maxitems reached'
end function
end
line 1 contains 5 items 3 are numbers
line 2 contains 5 items 3 are numbers
total lines is 2
您的代码实际上只计算三行。只因为m被初始化为1，并且在第二个循环中无论iostat错误是什么（这只是文件的结尾），都会递增，所以m才得到2。有点旁白，但在open语句中指定iostat，然后不检查值是一种糟糕的做法。在打开文件之前，您对文件的内容了解多少？它是否总是由
nm=m+1nm=m+1nn