I am trying to write a simple program to read down each column of the matrix and look for entries with a value of one. Since the matrix is of the format A i,j I want to program to write the i , j location for each value of one that it finds to a new file, Wires. Here is my code so far:. The program manages to read the first column where there is only a single entry with a value of 1. It writes the i , j position of this entry but otherwise I get an error that reads:. At line 25 of file conn-read.
After moving the open file statement I am still getting the same error. The line the error refers to contains the read statement. Depending on the layout of the contents of your input file and how you open it, you can probably read it in one line, like this:. If you've got your array stored in row-major order I expect that this quick and easy method will read it in the 'wrong' order, so you may want to transpose the array after reading it.
Or you may want to read it row by row rather like this:. These approaches will only work if there are the right number of integers in each row of the file and the right number of rows. And to answer your question: Yes, the error statement refers to the source line that was executing when the error occurred. The most likely causes of an unexpected end-of-file are that either the file isn't where the program is looking for it Fortran thinks of non-existent files as being almost the same as empty files or the file contains less data than you tried to read from it.
The cause of this latter error might be either that the file contains less data than you thought, or that your read statement s attempted to read more than you thought they did. I can't tell which is the case without seeing your input file. Whatever you do don't post your whole input file, but if you are still having problems post a snippet of it. I'm made suspicious that you haven't figured out entirely what is going on because you write The program manages to read the first column while your code, quite clearly, reads the values into the array row-by-row.
It may require more adjustment after this, but the first step is to move the open statement up, above the loops, like this:.
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Or you may want to read it row by row rather like this:. These approaches will only work if there are the right number of integers in each row of the file and the right number of rows. And to answer your question: Yes, the error statement refers to the source line that was executing when the error occurred. The most likely causes of an unexpected end-of-file are that either the file isn't where the program is looking for it Fortran thinks of non-existent files as being almost the same as empty files or the file contains less data than you tried to read from it.
The cause of this latter error might be either that the file contains less data than you thought, or that your read statement s attempted to read more than you thought they did.
I can't tell which is the case without seeing your input file. Whatever you do don't post your whole input file, but if you are still having problems post a snippet of it. I'm made suspicious that you haven't figured out entirely what is going on because you write The program manages to read the first column while your code, quite clearly, reads the values into the array row-by-row. It may require more adjustment after this, but the first step is to move the open statement up, above the loops, like this:.
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How to read a matrix and write certain values to a new file in Fortran Ask Question. Asked 9 years, 2 months ago. Active 3 years, 3 months ago. Viewed 21k times. It writes the i , j position of this entry but otherwise I get an error that reads: At line 25 of file conn-read. Improve this question. Vladimir F Take a few minutes to familiarise yourself with SO and how best to frame questions here. I, like many Fortran programmers, am too old and grumpy to assist people who don't make it as easy as possible.
Add a comment. Once done, it should be closed using the close statement. When the above code is compiled and executed, it creates the file data1. And then closes the file. The read and write statements respectively are used for reading from and writing into a file respectively. In this program we read from the file, we created in the last example, data1.
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