where construct 1

[mikibelavista]

I have problem that I have two arrays and I want to associate their arguments.But I have not managed this with where construct.
real,dimension(100) :: d,v
d has 6 different values,if d is 3,how to take all array elements of v?

 

[gummibaer]

I'd advise that you should clarify what you want to do.

You specify d to be an array of 100 elements, so d cannot be just 3.

And to get the elements of v from some file or keyboard input should not be affected by the type declaration and values of d at all.

Norbert


The optimist believes we live in the best of all possible worlds - the pessimist fears this might be true.

 

[xwb]

Not very sure of what you're trying to say. Could you write out what you are trying to do as a do loop? It is easier to convert to a where clause when you know what is required.

 

[mikibelavista]

I have solved this without where construct like this
sum1=0
n1=0
n2=0
do i=1,9
read(10,*)d(i)
read(11,*)v(i)
if (d(i)==3) then
s1=v(i)
n1=n1+1
sum1=sum1+s1
end if
if (d(i)==2) then
s2=v(i)
n2=n2+1
sum2=sum2+s2
end if
end do
av1=sum1/n1
av2=sum2/n2
write(*,*)sum1,sum2,n1,n2,av1,av2

 

[xwb]

It would have been easier without a where clause. The problem with the where clause is that non arrays cannot appear in it. You have to do something expensive like

program where1
integer d(9)
real    v(9)
real    s3(9), s2(9), n3s(9), n2s(9) 

read (10,*) d
read (11,*) v

! Initialize the counters
s2 = 0.0
s3 = 0.0
n2s = 0.0
n3s = 0.0

where (d .eq. 3)
   s3 = v
   n3s = 1.0
else where (d .eq. 2)
   s2 = v
   n2s = 1.0
end where
av1=sum(s3)/sum(n3s)
av2=sum(s2)/sum(n2s)
write(*,*)av1,av2 
stop
end

 

[xwb]

Alternatively use dot products, but still quite expensive

program where1
integer d(9)
real    v(9)
real    n3s(9), n2s(9)

read (10,*) d
read (11,*) v

! Initialize the counters
n2s = 0.0
n3s = 0.0

where (d .eq. 3)
   n3s = 1.0
else where (d .eq. 2)
   n2s = 1.0
end where
av1=dot_product(v,n3s)/sum(n3s)
av2=dot_product(v,n2s)/sum(n2s)
write(*,*)av1,av2
stop
end