Error when using the function "transpose" in Fortran

Question

I know that "transpose" in Fortran is an operator which flips a matrix over its diagonal. However, in the code below, I met an error and did not know why.

The code is:

program main
  implicit none
  real(8)::a(3,2),b(2,1)

  a=reshape((/1.0,2.0,3.0,4.0,5.0,6.0/),(/3,2/))
  b=reshape((/1.0,2.0/),(/2,1/))
  write(*,*)a(1,1:2)

  !Next sentence throw an error
  a(1,1:2)=transpose(b)
end program

The error is:

error #6366: The shapes of the array expressions do not conform. [A]

I think "a(1,1:2)" is one line and two columns, which is the same as "transpose(b)", why the compiler told me that "the shape do not conform"?

Should have searched first. I see I even have a deleted answer under the duplicate. — Vladimir F Героям слава, Jul 28 '17 at 14:19
Didn't even wait long enough to note that `real(8)` is ugly and not portable. — Vladimir F Героям слава, Jul 28 '17 at 14:21
Sorry because I just searched "Error transpose Fortran ", and didn't find the solution. Afterwards I will try some other key words such as error displays. — T X, Aug 02 '17 at 08:21
About the real(8) problem, I found this: [Fortran 90 kind parameter ](https://stackoverflow.com/questions/838310/fortran-90-kind-parameter). I will use "selected_real_kind" in the future. Thanks! — T X, Aug 02 '17 at 08:33
You are wrong, a(1,1:2) is not a 2D array (which you call a matrix), it is a 1D array. Bu using a(1,.. you are selecting a definite "row" in the "matrix" from which you take a "row vector" 1:2). You must use a(1:1,1:2) — Vladimir F Героям слава, Aug 02 '17 at 10:05
Yes, I thought I will delete the answer because of the duplicate, but I cannot delete an accepted answer. — Vladimir F Героям слава, Aug 02 '17 at 13:47

score 2 · Accepted Answer · answered Jul 28 '17 at 14:16

2

You are wrong, a(1,1:2) is not a 2D array (which you call a matrix), it is a 1D array.

Bu using a(1,.. you are selecting a definite "row" in the "matrix" from which you take a "row vector" 1:2).

You must use

a(1:1,1:2)

for a 2D array of shape 1x2 (matrix with one line and two columns if you want).

answered Jul 28 '17 at 14:16

Vladimir F Героям слава

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I will leave this here long enough for the OP to read the explanation directly about his code. – Vladimir F Героям слава Jul 28 '17 at 14:23
What's the difference between `real a(3)` vs `real b(1,3)`? What's the syntax of 2D Array constructor like `a = [1,2,3]`? @VladimirF – WhyMeasureTheory Oct 13 '21 at 19:10
1

`a(3)` is a 1D array of length 3, `b(1,3)` is a 2D array 1x3. There is no 2D array constructor, you can use `reshape()` https://stackoverflow.com/questions/3708307/how-to-initialize-two-dimensional-arrays-in-fortran – Vladimir F Героям слава Oct 13 '21 at 19:33
Aha, thanks @VladimirF. I am really going through a hard time because of FORTRAN. Coming from a high-level language to FORTRAN is really pathetic. – WhyMeasureTheory Oct 13 '21 at 19:38
It hasn't been called FORTRAN for more than 30 years. It is Fortran. And it is a high-level language (unlike assembly). – Vladimir F Героям слава Oct 13 '21 at 19:55

Error when using the function "transpose" in Fortran

1 Answers1