subroutine qform(m,n,q,ldq,wa) integer m,n,ldq double precision q(ldq,m),wa(m) c ********** c c subroutine qform c c this subroutine proceeds from the computed qr factorization of c an m by n matrix a to accumulate the m by m orthogonal matrix c q from its factored form. c c the subroutine statement is c c subroutine qform(m,n,q,ldq,wa) c c where c c m is a positive integer input variable set to the number c of rows of a and the order of q. c c n is a positive integer input variable set to the number c of columns of a. c c q is an m by m array. on input the full lower trapezoid in c the first min(m,n) columns of q contains the factored form. c on output q has been accumulated into a square matrix. c c ldq is a positive integer input variable not less than m c which specifies the leading dimension of the array q. c c wa is a work array of length m. c c subprograms called c c fortran-supplied ... min0 c c argonne national laboratory. minpack project. march 1980. c burton s. garbow, kenneth e. hillstrom, jorge j. more c c ********** integer i,j,jm1,k,l,minmn,np1 double precision one,sum,temp,zero data one,zero /1.0d0,0.0d0/ c c zero out upper triangle of q in the first min(m,n) columns. c minmn = min0(m,n) if (minmn .lt. 2) go to 30 do 20 j = 2, minmn jm1 = j - 1 do 10 i = 1, jm1 q(i,j) = zero 10 continue 20 continue 30 continue c c initialize remaining columns to those of the identity matrix. c np1 = n + 1 if (m .lt. np1) go to 60 do 50 j = np1, m do 40 i = 1, m q(i,j) = zero 40 continue q(j,j) = one 50 continue 60 continue c c accumulate q from its factored form. c do 120 l = 1, minmn k = minmn - l + 1 do 70 i = k, m wa(i) = q(i,k) q(i,k) = zero 70 continue q(k,k) = one if (wa(k) .eq. zero) go to 110 do 100 j = k, m sum = zero do 80 i = k, m sum = sum + q(i,j)*wa(i) 80 continue temp = sum/wa(k) do 90 i = k, m q(i,j) = q(i,j) - temp*wa(i) 90 continue 100 continue 110 continue 120 continue return c c last card of subroutine qform. c end