将向量插入矩阵的特定列 [英] Insert vector into matrix at specific columns

问题描述

如何将向量b插入列col的矩阵中?我在Fortran中找不到任何语法以及插入或追加函数.

How would I insert a vector b into a matrix at column col? I cannot find any syntax for and insert or append function in Fortran.

到目前为止，我所做的只是重新分配了列中的值，但我只想插入向量.

So far all I have done is reassigned the values in the column, but I only want to insert the vector.

real :: M(n,n)
integer :: n, col 
real :: b(n)
M(n:col) = b(:)

推荐答案

如果我了解您的问题，则希望:

If I understood of your problem, you want to:

• 将矩阵 m 的列数 n 增加1；
• 将向量 b 的内容作为新列插入 m 中的 col ;
• 右移 m 的其余列，以免丢失任何数据.

• increase the number n of columns of the matrix m by 1;
• insert the content of a vector b in m as a new column, at index col;
• right-shift the remaining columns of m, in order to not lose any data.

在这种情况下，您将需要注意以下几点:

Being this the case, you will need a couple of things:

如果要在本地更新数据，则
• 矩阵 m 必须是可分配的 .因此，如果您要返回一个新的独立数组，则不需要这样做(但是会创建一个额外的数据副本).
• 最好使用至少符合2003标准的编译器，这样您就可以访问固有的 move_alloc ，从而避免了在数组中复制一个数组.

• matrix m must be allocatable if you want to update the data locally. If you want to return a new independent array as a result, this wouldn't be necessary (but an additional data copy would be made).
• better use a compiler at least 2003 standard compliant so you have access to the intrinsic move_alloc, that avoid one array copy in the redimension.

这是一个演示实现:

program insert_vec
  integer, allocatable :: m(:, :), b(:)
  integer :: n = 3, col = 2, i
  allocate(m(n, n))
  allocate(b(n))
  m = 10
  b = [(i, i = 1, n)]
  call insert(m, b, col)
  do i = 1, n
      print *, m(i, :)
  end do
contains
  subroutine insert(m, b, col)
    integer, allocatable, intent(inout) :: m(:, :)
    integer, intent(in) :: b(size(m, 1)), col
    integer, allocatable :: temp(:, :)
    integer :: rows, cols
    rows = size(m, 1)
    cols = size(m, 2)
    allocate(temp(rows, cols + 1))
    temp(:, 1:col) = m(:, 1:col)
    temp(:, col) = b
    temp(:, col + 1:cols + 1) = m(:, col:cols)
    call move_alloc(temp, m)
  end
end

使用 gfortran 7.1.1 的输出是:

      10           1          10          10
      10           2          10          10
      10           3          10          10

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