using data from multiple files

[tatai]

I need to use data from three txt files. In file 1 there are 13 columns, in file 2 there are 3 columns and in file 3 there is 1 column.
I want to prepare a 4th file with
first 3 columns of file 1
1 column of file 2
1 column of file 3

I am opening all txt files (file1, file 2 and file 3) together. Reading the data using the while loop.
It is showing 'Build error' after run!

please help!

[vichu8888]

show your code please

[tatai]

#include<iostream>
#include<fstream>

using namespace std;

void main()
ifstream temp("temp.in");
	ifstream temp1("temp1.in");
	ifstream soil("soils.in");

	float col1, col2, col3, col4, col5, col6, col7, col8, col9, col10, col11, col12, col13, col14, col15;
	
		while(soil>>col1>>col2>>col3>>col4>>col5>>col6>>col7>>col8>>col9>>col10>>col11>>col12>>col13)
			while(temp>>col14)

I think i m doing mistakeby using two 'while' loop!! but do not understand how to solve it!!

[vichu8888]

Upto to my knowledge, if you put something inside the while brackets() , its a condition. So it just check and doesnt store values in the variables.

Sorry for the misguidance

[jlb]

There is noting wrong with putting the input inside the while parentheses, that is actually one of the preferred ways of reading input in a C++ program.

Really this program is screaming for the use of an array, or vector, possibly a structure.

Your problem is that you only have one of each of the variables, so if your file contains more than one you will have problems. I really recommend that you read each file in it's own loop, don't try to read multiple files in the same loop.

[tatai]

Jib

please expand!!! how can I read multiple file in same loop??

[jlb]

I said I don't recommend using the same loop. Use different loops to read each file.

[tatai]

Sorry!! I had mistyped!! If I am reading the files separately using the wile loop, then how I will merge the data(columns) from separate files into one??

[jlb]

If you are going to try to combine these three files into a third file, this is why I recommend using vectors to hold the data from the three files.

Please show a small sample of your three input files. And also a small sample of what the output file should look like.

[tatai]

EXAMPLE OF THE FILE:

file 1

1 2 1.2 2.5 3.6 3.66 4.55 8.1
5 10 1.2 3.2 5.6 3.33 4.25 8.1
25 rows

file 2

1.3
1.3
1.3

25 rows

file 3

7.8
7.8
7.8
25 rows

the output file (file4)

1 2 1.3 2.5 3.6 3.66 4.55 7.8
5 10 1.3 3.2 5.6 3.33 4.25 7.8
25 rows

[jlb]

In this case you can read all three files in a single while loop. I would recommend that you first read the information from the second or third file first, since they only contain one item per line. Something like:

float from3, from2;
float from1[SIZE]; // Where SIZE is a constant that corresponds to the number of items per line in file1. 
// open your files, make sure you insure the opening succeeded. 

while(file3 >> from3)
{
   file2 >> from2;
   if(!file2)
   {
       // Error reading from file 2 do something.
   }
   for(int i = 0; i < SIZE; ++i)
   {
      file1 >> from1[i];
   }
   if(!file1)
   {
       // Error reading from file 2 do something.
   }
   // Now write to your fourth file using the above information.
}

It is important to always check that your read and write operations succeed and if not either stop processing and tell the user about the problem or something else. But always check.