How to Extract Gridded Data in Fortran?

[jainax]

Hi,
Please bear with me on this because I'm really not a programmer at all but I need some help with modifying a code in fortran. This program is supposed to extract data for a single month of data at a time from the file highlighted in red below which contains 108 years of data. First of all, I would like to be able to call forth that file automatically without having to type it in everytime. I tried to put in a 'write' line to do that but when it came up in the program run, it didn't have the backslashes.
Second, rather than getting one month at a time, I would like to get all the months from a given year in each output file.
Lastly, the part at the bottom highlighted in green is dealing with latitudes. I only want to get latitudes within a certain range, which I've already plugged in. however, for the values i.gt.8.5, I don't want them to be included, so what do I have to put on the right side of that part to make that happen. Thanks in advance for any help anyone can offer!

Program read_gridded_all

integer valu(36,72)
integer i
integer imonth,jmonth,iyear,jyear
integer datachk
integer openfile
integer loopcnt
real lat,lon
character*110 infile,outfile
character*5 FMT100
character*6 FMT20

C INITIALIZE VARIABLES
datachk = 0
openfile = 0
loopcnt = 0

C ASK USER FOR INPUT GRID SET
write(*,*) 'Enter gridded dataset filename. '
C write(*,*) 'C:\Program Files\Force 2.0\grid_prcp_1900-2008.dat'
read(*,10) infile
C OPEN INPUT FILE
open(10,file=infile,status='old',err=500)
openfile = 1

C GRIDDED FILENAME NOT VALID
500 do while(openfile .eq. 0)
write(*,*) 'Cannot open ',infile
write(*,*) 'Reenter gridded dataset filename.'
read(*,10) infile
open(10,file=infile,status='old',err=500)
openfile = 1
enddo

C ASK USER FOR OUTPUT FILENAME
write(*,*) 'Enter output filename for gridded subset. '
read(*,10) outfile
C OPEN OUTPUT FILE
open(11,file=outfile)

C ASK USER FOR MONTH AND YEAR TO EXTRACT
write(*,*) 'Enter month to extract',
*'- integer format (1=>Jan, 2=>Feb, etc.)'
read(*,40) imonth
write(*,*) 'Enter year to extract'
read(*,40) iyear

10 format(a110)
40 format(i5)

FMT100 = '(2i5)'

write(*,*) 'Enter type of data, 1==>temp, 2==>prcp'
read(*,*) itype

if(itype.eq.1) then
FMT20 = '(12i5)'
else
FMT20 = '(12i7)'
endif

C LOOP OVER ALL MONTHS AND YEARS UNTIL FIND REQUESTED DATA
do while(datachk .ne. 1)
read(10,FMT100,end=900) jmonth, jyear
loopcnt = loopcnt + 1
C IF FOUND, THEN READ IN GRIDDED DATA
if(imonth .eq. jmonth .and. iyear .eq. jyear) then
write(*,50) imonth, iyear
50 format(' Reading gridded data for month ', i2.2,
*' and year ',i4)
do i = 1,36
do j = 1,6
read(10,FMT20) (valu(i,k),k=j*12-11,j*12)
enddo
enddo
C SET BOOLEAN TO TRUE
datachk = 1
C NOT CORRECT MONTH AND YEAR, SO SKIP GRIDDED DATA FIELDS
else
if(loopcnt.eq.1) then
write(*,110) imonth,iyear
110 format(' Searching for month ', i2.2, ' and year ',i4)
endif
do i = 1,216
read(10,*)
enddo
endif
enddo

C WRITE DATA TO OUTPUT FILE
write(*,*)'Writing output data to file'
do i = 1,36
if(i.le.8.5) lat = 92.5 - i * 5.0
elseif(i.gt.8.5) lat = ((i-18) * (-5.0)) + 2.5
do j = 1,72
if(valu(i,j) .ne. -9999) then
if(j.le.36) lon = (182.5 - (j * 5.0)) * (-1)
if(j.gt.36) lon = ((j-36) * 5.0) - 2.5
write(11,30) lat,lon,valu(i,j)/100.
endif
enddo
enddo

C CLOSE INPUT AND OUTPUT FILES
close(10,err=540)
close(11,err=560)

GO TO 999

30 format(f6.1,2x,f7.1,2x,f8.2)

540 write(*,*) 'Cannot close ',infile
560 write(*,*) 'Cannot close output file'
900 write(*,*) 'Requested Data Not Available!'
write(*,*) 'Sorry - Try Again. Exiting Program!'

999 STOP
END

 

[mgb_phys]

It looks like a problem with putting the file names in.
Possibly due to \char meaning something - in 'C' you would either use / or \\ to escape.
Sorry it's been a lot of years, back when I did fortran you only had numbered streams and had to associate a file with the stream before running the program.

I would suggest you write a very small program just attempting to open a file that will let you trace the problem without positing lots of other parts of the code that aren't relevant.

 

[jainax]

I doubled the slashes and now it's showing up properly in the program but it's still not reading it. Howevever, if I type in the exact same thing manually, it works.

 

[mgb_phys]

That's my point, in 'C' if you have "c:\test" the \t is interpreted as a tab character by the compiler - its the only way to put code characters inside a string. When you type in the string to a running program it isn't seen by the compiler so control chars aren't expanded.

I don't know about string literals in Fortran but I suspect they have a similair mechanism. In windows you can use the forward slash / to avoid this.

 

[zeitghost]

 do i = 1,36
if(i.le.8.5) lat = 92.5 - i * 5.0
elseif(i.gt.8.5) lat = ((i-18) * (-5.0)) + 2.5
do j = 1,72

Isn't "i" an integer?

You appear to be comparing it with a real number (floating point)...

Dunno if that'll make any difference, but it used to do strange things in FORTRAN IV...

 

[alphysicist]

Hi jainax,

These lines do not seem to have the right form:


if(i.le.8.5) lat = 92.5 - i * 5.0
elseif(i.gt.8.5) lat = ((i-18) * (-5.0)) + 2.5

With them like that, the elseif is a separate statement, which is not allowed. The following are three different ways you could do this:

if(i.le.8.5) lat = 92.5 - i * 5.0
if(i.gt.8.5) lat = ((i-18) * (-5.0)) + 2.5



if(i.le.8.5) then
    lat = 92.5 - i * 5.0
elseif(i.gt.8.5) then 
    lat = ((i-18) * (-5.0)) + 2.5
endif


if(i.le.8.5) then
    lat = 92.5 - i * 5.0
else
    lat = ((i-18) * (-5.0)) + 2.5
endif

 

[mgb_phys]

540 write(*,*) 'Cannot close ',infile
560 write(*,*) 'Cannot close output file'
900 write(*,*) 'Requested Data Not Available!'

Oops sorry, I forgot that you didn't need goto lables in fortran.
I thought these were the error messages when you ran it, not part of the code!
That's why I mentioned the problem with the filenames.