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arctica
Joined: 10 Sep 2006
Posts: 146
Location: United Kingdom
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 Posted: Thu Jun 04, 2020 10:17 am Post subject: Write array to X,Y formatted file |
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Hello,
I am trying to write X,Y values to a file from a 2D array, but the data does not output correctly in 2 columns for X and Y. At present in writes X as 2 columns and then Y appended on the end. How to write X to col 1 and Y to col 2. Sorry if this is a basic query - using ftn95.
| Code: |
program linear_test
! Purpose: create X and Y 2D arrays
! write file with 2 columns X,Y of 120x120 (14400) values
! z-data has same geometry
implicit none
real :: dxy, xmin, xmax, xrange, ymin, ymax, yrange
integer :: npoints, i, sv, nx, ny, xydim
real,allocatable :: xx(:), yy(:)
real, allocatable :: X(:,:), Y(:,:)
open (25, file='xy-data.dat', status='new') ! open new file for write
npoints=120
allocate(xx(npoints))
xmin = -5.0
xmax = -3.0
allocate(yy(npoints))
ymin = -5.0
ymax = -3.0
xrange = xmax - xmin
!yrange = ymax - ymin
! Linspace
dxy = xrange / real(npoints-1) ! calculate increment
do i = 1,npoints
xx(i) = xmin + (i-1)*dxy
yy(i) = ymin + (i-1)*dxy !same increment in y
end do
sv=0
nx = size(xx, dim=1)
ny = size(yy, dim=1)
xydim = nx*ny
allocate(X(ny,nx),Y(ny,nx),stat=sv)
allocate(X1(xydim),Y1(xydim),stat=sv)
! Meshgrid
X(1,:) = xx
X(2:ny,:) = spread(xx, dim=1, ncopies=ny-1)
Y(:,1) = yy
Y(:,2:nx) = spread(yy, dim=2, ncopies=nx-1)
! write 2 columns (X,Y)
write (25,'(f15.10,f15.10)') X, Y
deallocate(xx,yy,X,Y)
close(25)
end program linear_test
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The code is fine if I just want X or Y and generates the 14400 values expected.
Thanks for any pointers
Lester |
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mecej4
Joined: 31 Oct 2006
Posts: 1899
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| Posted: Thu Jun 04, 2020 10:33 am Post subject: |
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The IOlist in the WRITE statement that you wrote is not suitable for your desired output. Instead, use
| Code: | | write (25,'(f15.10,f15.10)') (X(i), Y(i), i=1, npoints) |
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arctica
Joined: 10 Sep 2006
Posts: 146
Location: United Kingdom
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| Posted: Thu Jun 04, 2020 11:02 am Post subject: Re: |
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Many thanks for the pointers. The X and Y are 2D arrays so just had to tweak the line:
| Code: | | write (25,'(f15.10,f15.10)') (X(i,:), Y(:,i), i=1, npoints) |
Currently re-learning Fortran 95; been a while!
| mecej4 wrote: | The IOlist in the WRITE statement that you wrote is not suitable for your desired output. Instead, use
| Code: | | write (25,'(f15.10,f15.10)') (X(i), Y(i), i=1, npoints) |
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mecej4
Joined: 31 Oct 2006
Posts: 1899
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| Posted: Thu Jun 04, 2020 11:20 am Post subject: |
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Right, I overlooked the fact that you had X as well as XX as variables (also Y and YY).
Your modified WRITE statement will still print:
nx elements of X(1,:), two per line,
ny values of Y(:,1), two per line,
and repeats this pattern for i = 2:npoints. This may not be what you wanted. |
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JohnCampbell
Joined: 16 Feb 2006
Posts: 2615
Location: Sydney
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| Posted: Wed Jun 10, 2020 8:59 am Post subject: |
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"write (25,'(f15.10,f15.10)') X, Y"
This is equivalent to:
write (25,'(f15.10,f15.10)') (X(i,j),i=1,ny,j=1,nx), (Y(i,j),i=1,ny,j=1,nx)
If you don't like it then re-order the implied do in the write. I presume you wanted:
write (25,'(f15.10,f15.10)') ( X(i,j),Y(i,j), i=1,ny, j=1,nx)
I find an explicit do is more flexible.
Not a very readable list though. Perhaps the following would be more useful.
write (25,'(2i5,2f15.10)') ( i,j,X(i,j),Y(i,j), i=1,ny, j=1,nx)
For Meshgrid, you could write: | Code: | do i = 1,nx
X(:,i) = xx(i)
Y(:,i) = yy(:)
end do |
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JohnCampbell
Joined: 16 Feb 2006
Posts: 2615
Location: Sydney
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| Posted: Mon Jun 15, 2020 2:52 pm Post subject: Re: |
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| John-Silver wrote: | | Even Fortran 77 satisfies the vast majority of Fortraneers, especially those of Anglo-Romanic descent ;-) |
Don't think many would agree with that. No Allocate! or System_Clock and lots of others.
Yes, I was wrong with my brackets !!
It should be: write (25,'(f15.10,f15.10)') ( ( X(i,j),Y(i,j), i=1,ny ), j=1,nx )
"write (25,'(f15.10,f15.10)') ( ( X(i,j),Y(i,j) ) , i=1,ny, j=1,nx)" is no go either.
It could become write (25,'(f15.10,f15.10)') ( ( X(i,j) ) , i=1,ny, j=1,nx) |
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mecej4
Joined: 31 Oct 2006
Posts: 1899
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| Posted: Thu Jun 25, 2020 4:00 pm Post subject: |
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John S., you wrote
| Quote: | | write (25,'(f15.10,f15.10)') ( ( X(i,j),Y(i,j) ) , i=1,ny, j=1,nx) |
The extra pair of parentheses is a no-no because within those parentheses are present two expressions with a comma in between. The expression (E1,E2), where E1 and E2 are constants of numeric type, is a complex constant. When E1 or E2 is not a literal constant, CMPLX(E1,E2) would give you a complex valued expression. Without CMPLX, what does (E1, E2) mean? In Fortran the integrity of parentheses in expressions has to be guarded, so the parentheses must have a purpose, but what the dickens is it? What would the following mean:
| Code: | | write (25,'(f15.10,f15.10)') ( ( X(i,j),Y(i,j), Z(i,j) ) , i=1,ny, j=1,nx) |
Apart from the issue of extra parentheses, what about the implied DO loops? Is the i-loop inside the j-loop, or the other way?
You also wrote:
| Quote: | | but I'm sure they have their reasoning for their sometimes counter-intuitive decisions |
Relying on intuition or Anglo-Romanic descent to resolve this question in this narrow context is almost certain to create huge problems in other parts of the language. Most of us are not far-sighted enough to see through the ramifications of changing the language just to mollify an itch of the moment. |
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