Help with declaring arrays in Fortran 90/95

In summary, the conversation is about creating a program that calculates the least squares fit line to a set of points. The person is struggling with how to read in an arbitrary number of points from the user. They initially planned to have the user enter the number of elements and then create an array with that many elements, but this approach is not allowed in Fortran. They discuss using allocatable arrays as a solution and suggest researching the syntax.
  • #1
warfreak131
188
0
I have an assignment to calculate the least squares fit line to a set of points, and I have to read in an arbitrary number of points from the user

So my plan was to have the user enter how many elements they have, and then create an array with that many elements. So let's say I read the value N from the user, and then create an array like:

Code: 
real, dimension(N) :: xvals, yvals

But that's a no-no according to fortran. If any read/write statement goes before declaring the variables, I get a whole host of errors. However, if I remove those read/write statements and create a set number of array elements like:

Code: 
real, dimension(10) :: xvals, yvals

then all the error go away. Unfortunately, I have to find out how many variables the user wants before creating the array.
 
Technology news on Phys.org
  • #2
You need to learn how to use allocatable arrays. Googe it and learn the syntax. It is pretty easy.
 

FAQ: Help with declaring arrays in Fortran 90/95

What is an array in Fortran 90/95?

An array in Fortran 90/95 is a data structure that allows you to store multiple values of the same data type in a single variable. It can be thought of as a collection of elements arranged in a specific order.

How do I declare an array in Fortran 90/95?

To declare an array in Fortran 90/95, you need to specify the data type of the elements, the number of dimensions, and the size of each dimension. For example, to declare a 1-dimensional array of integers with 10 elements, you would use the syntax: integer :: my_array(10).

Can I declare an array with a variable size in Fortran 90/95?

Yes, you can declare an array with a variable size in Fortran 90/95 using the ALLOCATABLE keyword. This allows you to dynamically allocate memory for the array at runtime, based on the value of a variable.

How do I access elements of an array in Fortran 90/95?

You can access elements of an array in Fortran 90/95 by specifying the index values within parentheses after the array name. For example, to access the third element of an array called my_array, you would use my_array(3).

Can I use loops with arrays in Fortran 90/95?

Yes, you can use loops with arrays in Fortran 90/95 to perform operations on multiple elements of the array. This is a powerful feature of arrays that allows you to efficiently process large amounts of data.

Similar threads

Fortran Dimension of arrays (RESHAPE) in Fortran 90
Replies
4
Views
2K
Fortran Fortran 90/95: Array Help with IF Statement
Replies
2
Views
1K
Fortran Errors in Fortran code for solving Laplace's equation in 3D
Replies
4
Views
2K
Fortran Assign 2D Array with Reals in Fortran - Help Needed
Replies
4
Views
2K
Fortran Fortran 90: Display values in an array
Replies
13
Views
2K
Fortran [FORTRAN] Assigning bad values in arrays
Replies
13
Views
2K
Fortran Can complex numbers be used in Fortran array constructors?
Replies
5
Views
9K
Fortran Fortran, passing an array to multiple subroutines
Replies
5
Views
3K
How to read a column of data into Fortran without arrays? (Fortran 77)
Replies
7
Views
2K
Fortran Fortran (90) runtime error: End of file
Replies
19
Views
6K

Hot Threads

Recent Insights

Back
Top