Question

I have the following data

X     Y    INFTIME
1     1     0
1     2     4
1     3     4
1     4     3
2     1     3
2     2     1
2     3     3
2     4     4
3     1     2
3     2     2
3     3     0
3     4     2
4     1     4
4     2     3
4     3     3
4     4     0

X and Y represent he X and Y components in the square grid of 4 by 4.
Here I want to sample randomly 10% from the population which are infected i.e, whose INFTIME is non zero. I did not get any idea of coding so could not start it.
Any suggestions and idea will be great for me.
Thanks

EDIT:

DO T = 1,10
   DO i = 1, 625

      IF(INFTIME(i)/=0 .AND. INFTIME(i) .LE. T)THEN
         CALL RANDOM_NUMBER(u(i))
         u(i) = 1+aint(u(i)*25)
          CALL RANDOM_NUMBER(v(i))
         v(i) = 1+aint(v(i)*25)
          CALL RANDOM_NUMBER(w(i))
         w(i) = 1+aint(w(i)*10)
      ENDIF
   ENDDO
ENDDO


do p = 1,625
  WRITE(*,*) u(p),v(p),w(p)
 enddo

This is my code what I tried but it only gives the random numbers, not the connection to the data. I used the data of 25 by 25 grids i.e, 625 individuals and time of infection 1 to 10

Answer 1

Follow what ja72 said. You have three 1D arrays of the same size (16). All you need to do is pick a number between 1 and 16, check to see if INFTIME is zero and accept the value as needed, then repeat until you’ve taken 10% of the samples (which would be 1.6 values, so I presume you’d just take 2? Or do you have more data than this 4×4 you presented?)

Edit You need to call the random number generator before the if statement:

    do t=1,10
      do i=1,625
          ind = 1+int(624*rand(seed))
          if(inftime(ind).neq.0 .and. inftime(ind).le.t) then
             stuff
          endif
       enddo
    enddo

The call ind=1+int(625*rand(seed)) will pick a random integer between 1 (when rand(seed)=0) and 625 (when rand(seed)=1). Then you can do what you need if the if statement is satisfied.

EDIT: program epimatrix

IMPLICIT NONE
INTEGER ::l, i,T,K
REAL, DIMENSION(1:625):: X,y,inftime
INTEGER::seed,my_cnt
INTEGER,DIMENSION(8) :: time1
CALL DATE_AND_TIME(values=time1)
seed = 1000*time1(7)+time1(8)
call srand(seed)

OPEN(10, FILE = 'epidemicSIR.txt', FORM = 'FORMATTED')
DO l = 1,625
   READ(10,*,END = 200) X(l), Y(l), INFTIME(l)
  ! WRITE(*,*) X(l),Y(l), INFTIME(l)
  ! if you know how it was formatted, you should use
  ! read(10,20) X(l), Y(l), INFTIME(l)
  ! where 20 is the format
ENDDO
200 CONTINUE
CLOSE(10)

DO T = 1,10
   my_cnt=0
   write(*,*) "T=",T
   DO while (my_cnt.le.63)
      K = 1+int(624*rand())
      IF(INFTIME(K)/=0 .AND. INFTIME(K) .LE. T)THEN
         write(*,*) X(k),Y(k),INFTIME(k)
         my_cnt=my_cnt+1
      ENDIF
   enddo
   write(*,*) " "
ENDDO

end program

EDIT 2
I’ve adjusted the program to fix some of the issues. I’ve tried keeping my edits in lowercase so that you can see the difference. The do-while loop allows the code to continue running until the condition my_cnt.le.63 has been met (which means you have 63 lines of X, Y, inftime per T). I’ve added a line to output T and another line to add a space so that the data might be more clear when looking at the output.

This should take care of all the issues you’ve been running into. If not, I’ll keep checking this page.