Help with C++ file matrix program

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  1. #1
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    Exclamation Help with C++ file matrix program

    Hello
    I am writing a program that is supposed to read from an input txt file values into a 2d array.
    The file has about 13500 lines of 75 values each, separated by spaces. at the end of each line there is no space, just '\n'
    I need to make some operations with the values in the file, so I will have to read the file into a 2d array.
    The thing is, because of the end of line not having a space character, I am having alot of trouble reading the values into the array.
    Can anyone help me?

    Code:
    #include "stdafx.h"
    #include <iostream>
    #include <conio.h>
    #include <time.h>
    #include <fstream>
    #include <cstdlib>
    #include <istream>
    #include <iomanip>
    #include <sstream>
    #include <string>
    #include <stdio.h>
    #include <stdlib.h>
    #include <math.h>
    using namespace std;
    #define SCREEN_HEIGHT 50
    
    
    fstream datafile;                 /*Original data file*/
    ofstream outputfile;
    string infilename,outfilename,A[13316][75],line;
    int option,menuin,menuout,menualg,number_of_lines,col;
    double matrix[13316][75],sum=0;
    
    
    void clrscr()
    {
        int i;
        for ( i = 0; i < SCREEN_HEIGHT; i++ )
            putchar ( '\n' );
    }
    
    
    int readfromfile()                                /*Reads the first line of the file into variable "line"*/
    {
        if (datafile.is_open())
        {
            getline (datafile,line);
            datafile.close();
        }
        return 0;
    }
    
    
    int writetofile ()                                /*Test function. Writes "line" to the output file.*/
    {
        cout << "\nThe line\n \n" << line << "\n\nwas copied variable line" << endl;/*Gives feedback of the copied line to user.*/
        return 0;
    }
    
    
    string Inputfilename()
    {
        clrscr();
        cout << "What is the name of your data input file?\n";
        cin >> infilename;
        datafile.open(infilename);
        while(!datafile)
            {
                cout << "Filename invalid. Try again!\n";
                cin >> infilename;
                datafile.open(infilename);
            }
        if (datafile)            /*Verificare existenta fisier*/
            {
                cout << "Filename saved. Press any key...\n";
                getchar();
            }
        return infilename;
    }
    
    
    string Outputfilename()
    {
        clrscr();
        cout << "What is the name of your data output file?\n";
        cin >> outfilename;
        outputfile.open(outfilename);
        while(!outputfile)
            {
                cout << "Filename invalid. Try again!\n";
                cin >> outfilename;
                outputfile.open(outfilename);
            }
        if (outputfile)        /*Verificare existenta fisier*/
            {
                cout << "Filename saved. Press any key...\n";
                getchar();
            }
        return outfilename;
    }
    
    
    int linesinfile()                            /*Calculates the number of lines in datafile(the number of rows in matrix)*/
    {
        datafile.open(infilename);
        cout << "Computing number of rows...\n";
        number_of_lines=0;
        std::string liney;
        while (std::getline(datafile, liney))
        {
            ++number_of_lines;
        }
        datafile.close();
        std::cout << "Number of rows is: " << number_of_lines <<"\n";
        return number_of_lines;
    }
    
    
    int columns()                            /*Calculates the number of columns in datafile*/
    {
        datafile.open(infilename);
        cout << "Computing number of columns...\n";
        col=0;
        for (int i=0;i<=line.size();i++)
            if (line[i]==' ')
                col++;
        col = col++;
        datafile.close();
        cout << "Number of columns is: " << col <<"\n";
        return col;
    }
    
    
    int Algorythm(int N, int M)
    {
        clrscr();
        datafile.open(infilename);
        if(!datafile) //Always test the file open.
        {
                    cout << "Error opening output file" << endl;
                    system("pause");
        }
        cout << "Reading file to a string matrix...\n";
        while(!datafile.eof())
        {
            for(int R=0;R<N;R++)
                for(int C=0;C<M;C++)
                    getline(datafile,A[R][C],' ');
        }
    
    
        cout << A[0][74];
        /*cout << "Converting string matrix to a double matrix...\n";
        for(int R=0;R<N;R++)
            for(int C=0;C<M-1;C++)
                matrix[R][C] = atof(A[R][C].c_str());
        for(int i=0;i<M-1;i++)
            cout << A[0][i] << "\n";
        cout << A[1][0];
        
        getchar();
        cout << "Writing the matrix as double in the output\n";
        outputfile.open(outfilename);
        for(int R=0;R<N;R++)
                for(int C=0;C<M;C++)
                {
                    matrix[R][C] = stod( A[R][C] );
                    outputfile << matrix[R][C] << ' ';
                }
        outputfile.close();*/
        return 0;
    }
    
    
    int main()
    {
        cout << "This program reads the 0.3 step data from an input file and generates an output file with 3 step data.\nPress any key to start...\n";
        Inputfilename();
        Outputfilename();
        readfromfile();
        columns();
        linesinfile();
        Algorythm(number_of_lines,col);
        getchar();
        return 0;
    }

  2. #2
    Frequently Quite Prolix dwks's Avatar
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    It's really quite straightforward. C++ considers all whitespace (spaces, newlines) to be separating characters, so if you say
    Code:
    int x;
    while(file >> x) {
        std::cout << "I got " << x << std::endl;
    }
    you'll get in turn each number in the file. If you want to stop reading at the end of a line, just grab the whole line and make a new stream out of it. Here's a working example. I read from std::cin but you could just as easily read from a file.
    Code:
    $ cat matrix.cpp
    #include <iostream>
    #include <sstream>  // string stream stuff
    #include <string>
    
    int main() {
        std::string line;
        while(std::getline(std::cin, line)) {
            std::istringstream stream(line);  // needs #include <sstream>
            int x;
            while(stream >> x) {
                std::cout << "[" << x << "]";
            }
            std::cout << std::endl;
        }
        return 0;
    }
    $ cat matrix.txt
    1 2 3 4
    5 6 7 8
    $ ./matrix < matrix.txt
    [1][2][3][4]
    [5][6][7][8]
    $
    In case you're not familiar with UNIX commands, that's just me showing you the source code, the input file, and then the program run with the input file.

    So from there it's pretty straightforward to build a 2D array, I think. Do you agree? One last point: if you use std::vector then you don't have to worry about e.g. counting the number of lines in advance.

    [edit] Hint:
    Code:
    for(i = 0; std::getline(file, line); i ++) {
        std::istringstream stream(line);
        for(j = 0; stream >> x; j ++) {
            array[i][j] = x;
        }
    }
    [/edit]
    Last edited by dwks; 12-09-2012 at 04:02 PM.
    dwk

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  3. #3
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    I don't want the program to stop reading at the end of a line. I need the numbers to go into a matrix. As I said, I need to make some calculations with the numbers afterwards. So the matrix is a must. And I don't want the program to stop reading at end of line.
    Here is a generic example of the format of my file:

    value1.1[space]value1.2[space]...[space]value1.75[\n]
    value2.1[space]value2.2[space]...[space]value2.75[\n]
    .................................................. .......................
    value13315.1[space]value13315.2[space]...[space]value13315.75[\n]
    value13316.1[space]value13316.2[space]...[space]value13316.75[\n]

    The program should read these values in a matrix as follows:
    A[1][1]=value1.1 and so on.

    The problem with the program I wrote is when the matrix reading counter reaches the end of the first line it should read A[1][75]=value1.75 and A[2][1]=value2.1. Instead it reads into A[1][75] "value1.75\nvalue2.1" because the getline used in the counter uses ' '(space character) as a separator and does not recognize the \n character as being a separator and just keeps reading until it reaches the ' ' in the second line. You can imagine how that messes up the entire matrix.

    I am not an advanced C++ user, so I did not understand what your latter examples did.
    My question is can I modify my existing code in order for it to do what I want or do I have to use more advanced C++ coding?

  4. #4
    Frequently Quite Prolix dwks's Avatar
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    Quote Originally Posted by tempester86 View Post
    I don't want the program to stop reading at the end of a line. I need the numbers to go into a matrix.
    Perhaps that was badly worded. What I meant was, you want the program to realize when it reaches the end of a line so that it can go onto the next row of the matrix. Essentially, reading in all the numbers as just a single sequence is very easy, but you want to know where the line-ends are so that you end up with a matrix, not a super-huge vector.

    The problem with the program I wrote is when the matrix reading counter reaches the end of the first line it should read A[1][75]=value1.75 and A[2][1]=value2.1. Instead it reads into A[1][75] "value1.75\nvalue2.1" because the getline used in the counter uses ' '(space character) as a separator and does not recognize the \n character as being a separator and just keeps reading until it reaches the ' ' in the second line. You can imagine how that messes up the entire matrix.
    What you are doing is far more work! You're reading in stuff as strings and then converting to numbers later on. Why not just read in numbers directly?

    Look, maybe another example will make things clearer.
    Code:
    #include <iostream>  // for cout, getline
    #include <fstream>  // for ifstream
    #include <sstream>  // for istringstream
    #include <string>   // for string
    
    int main() {
        std::ifstream file("data.txt");  // assume the file opens correctly
    
        int matrix[10][10];
        int row = 0, col = 0;
    
        std::string line;
        while(std::getline(file, line)) {  // read each line from the file
            // okay we have a line, let's extract the numbers on this line
            // this is an "input string stream", a stream formed from a string
            std::istringstream stream(line);
    
            int x;
            col = 0;  // reset column counter
            while(stream >> x) {  // keep trying to read ints until there are no more
                matrix[row][col] = x;
                col ++;
            }
    
            // okay that's all the data on this line, go to the next line
            row ++;
        }
    
        // now let's print out the data we read into the matrix.
        // At this point, row tells us how many rows there are, and
        // we never reset col so col still tells us how many values were on
        // the last line (let's hope this is the same as the other rows of the
        // matrix).
        for(int i = 0; i < row; i ++) {
            for(int j = 0; j < col; j ++) {
                std::cout << '(' << matrix[i][j] << ") ";
            }
            std::cout << "\n";
        }
        return 0;
    }
    If I have this in data.txt
    Code:
    1 2 3 
    4 5 6 
    7 7 8 
    3 2 1
    then when I run the program I see this as output:
    Code:
    (1) (2) (3) 
    (4) (5) (6) 
    (7) (7) (8) 
    (3) (2) (1)
    I print parentheses around the numbers so that you can see it really did parse them into the matrix, otherwise the output looks identical to the input.

    This isn't really very advanced C++ coding. It's very standard stuff for processing text files. You might be able to hack something else together for now but you'll still have trouble reading files as input later on. Might as well make an attempt at learning some of this now. You can ask specific questions if you don't understand, or go looking for other material online. But to be honest your code is a bit of a mess... I mean why are you doing this?
    Code:
    getline(datafile,A[R][C],' ');
    If you want to read ints, just say "datafile >> x" and be done with it. Why is A an array of an array of strings? Aren't matrices usually numbers? And so on.

    [edit] Re-reading your input file format again, I'm wondering if you actually see the string "value" in your file over and over again... that would be kind of strange, but if you do you could just call stream.get() repeatedly until you see (say) an 'e', and then read a number with "stream >> x". [/edit]
    Last edited by dwks; 12-12-2012 at 04:33 PM.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


    Other boards: DaniWeb, TPS
    Unofficial Wiki FAQ: cpwiki.sf.net

    My website: http://dwks.theprogrammingsite.com/
    Projects: codeform, xuni, atlantis, nort, etc.

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