Problem on reading dataset with variable decimal places as it is using fortran

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Discussion Overview

The discussion revolves around reading a dataset with variable decimal places into a real array using Fortran and the challenges associated with preserving the original formatting of the data when writing it back to a file. The scope includes technical explanations and programming challenges related to data handling in Fortran.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes their attempt to read a tab-delimited text file into a real array and notes that the output format changes the number of decimal places to three.
  • Another participant explains that when data is read, it is converted from decimal to binary, which does not retain the original decimal formatting.
  • It is suggested that to preserve the original number of decimal places, the data should be read as character strings and then converted to numeric data using Fortran's internal read technique.
  • A participant shares a code snippet that demonstrates reading a character string and converting it to a real number, but notes that the output still does not match the original formatting.
  • Another participant reiterates the importance of writing the original character variable back out instead of the internal real variables to maintain the original formatting.

Areas of Agreement / Disagreement

Participants express differing views on how to handle the formatting issue, with some suggesting character string methods while others emphasize the importance of outputting the original data. The discussion reflects a lack of consensus on the best approach to preserve the original decimal formatting.

Contextual Notes

The discussion highlights limitations related to the handling of decimal places in Fortran, particularly the conversion from decimal to binary and the implications for output formatting. There are unresolved aspects regarding the effectiveness of the proposed solutions.

fortranuser
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Hi all,
I have attached my text file(tab delimited).
I am planning to read those dataset into real array of (30,38). The dataset has variable decimal places like 312.66, 0, 535.696 ,456122.758.
With the following codes,
READ(12,*)((X(I,J),I=1,30),J=1,38)

WRITE(*,20)((X(I,J),i=1,30),j=1,38)

20 format(58(f12.3x,2x))

I was able to read the original txt file and stored those data into real array of (30,38) and then it was written in new txt file.

The problem is that because of the format(58(f12.3x,2x)) the data set in latter file got changed(now each data set has 3 decimal places)
Is it possible to make data in latter file similar to original text file
 
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When you read the original data, it's converted from decimal to binary and stored as binary inside your program. The binary data has no "memory" of the original number of decimal places.

If you really need to preserve the original number of decimal places on output, you should read the data as character strings, then convert the strings to binary numeric data using Fortran's "internal read" technique. Do your calculations using the converted data, but write the original data back out using the character strings.
 
jtbell said:
When you read the original data, it's converted from decimal to binary and stored as binary inside your program. The binary data has no "memory" of the original number of decimal places.

If you really need to preserve the original number of decimal places on output, you should read the data as character strings, then convert the strings to binary numeric data using Fortran's "internal read" technique. Do your calculations using the converted data, but write the original data back out using the character strings.

hi jtbell,
Thanks for writing me. I have written the program just to test which is as follow
PROGRAM CHAR_ARRAY

character(10):: data
real::a
read(*,*)data
read(data,*)a
print*,a
END
I gave 45.2 to data and output was 45.200001.
so still the problem is same.
 
Well, what jtbell said was to write the original data back out by using the original 'character' variable you read it into...not using your internal 'real' variables.
 
gsal said:
Well, what jtbell said was to write the original data back out by using the original 'character' variable you read it into...not using your internal 'real' variables.

hi gsal
I carefully read to jtbell again and finally understood what you and he wants me to do.
Thanks both of you.Problem is no more.
 

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