How to read numbers from a txt file in C#?

Question

This is an example file:

2
0.03159527 0.1990048 0.9794891
0.02173799 0.9969404 0.07508247

The first number indicates how many lines are, for each line are always three numbers

I tried to do something like this:

    Vector3[] Load()
{
    StreamReader entrada = new StreamReader ("gestos_saida.txt");

    int size = entrada.Read ();
    Vector3[] v = new Vector3[size];
    for (int i = 0; i < size; i++)
    {
        float x, y, z;
        x = entrada.Read ();
        y = entrada.Read ();
        z = entrada.Read ();
        v[i] = new Vector3 (x, y, z);
    }

    entrada.Close ();
    return v;
}

But the numbers read do not match the file, as I can read these numbers without using a ReadLine() and then break the string?

Answer 1

You can’t, you have to be manual. You have to read the lines, break the data and convert it. I considered that the file will always be well formatted and with correct data. Something like this:

using System;
using static System.Console;
using System.IO;

public class Program {
    public static void Main(string[] args) {
        var texto = "2\n0.03159527 0.1990048 0.9794891\n0.02173799 0.9969404 0.07508247";
        using (var reader = new StringReader(texto)) { //só trocar para o arquivo aqui
            int size = int.Parse(reader.ReadLine());
            for (int i = 0; i < size; i++) {
                string[] linha = reader.ReadLine().Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
                WriteLine($"{linha[0]}, {linha[1]}, {linha[2]}"); //depois troca para o Vector3
            }
        }
    }
}

Behold working ideone. And in the .NET Fiddle. Also put on the Github for future reference.

Answer 2

I understand your logic. You want to store text value information for three-element vectors. I just don’t understand if you want to do this to generate a single vector or want to store multiple vectors, but surely both cases are possible. You just need to define a logic for your text. If you store an immutable fixed number of vectors of three numbers, you can store everything in a 3x matrixn, where n is the number of column vectors to be stored (in this case as specified as the first number in the text file). I call it "matrix" for its concept of linear algebra, but it is nothing more than a array vector, so it will be a vector type[n], as apparently is what you want.

Let’s assume that you want to store everything in an array. In this implementation, what we would do is:

1. Read the first line to define the dimensions of a matrix (array of vectors);
2. Read each row of three numbers divided by spaces;
3. Divide each string between its spaces;
4. Fill in the template with strings obtained by converting them to float or double (depending on the accuracy you want).

Below is the detailed implementation:

using System;
using System.Linq;

namespace Programa
{
      public class Program
      {
            Vector3[] Load(string filePath)  // Endereço do arquivo
            {
                Vector3[] v;
                using (StreamReader sr = new StreamReader(filePath))
                {
                    string[] linha;
                    float[] nrs = new float[3];
                    int size = int.Parse(sr.ReadLine());  // Leio a primeira linha apenas, com o número de vetores da matriz
                    int i = 0;
                    v = new Vector3[size];

                    while (!sr.EndOfStream && i < size)
                    {
                        linha = sr.ReadLine().Split(' ');  // Divido pelos espaços
                                                           // Veja as outras sobrecargas de Split para mais opções
                        nrs = linha.Select(n => float.Parse(n)).ToArray();  // Uso Linq para selecionar cada elemento e converter para float
                        v[i] = new Vector3 (nrs[0], nrs[1], nrs[2]);
                        i++;
                    }
                }
                return v;
            }
      }
}

Instead of float. Parse, use double.Parse for double decimal precision if desired. Also, always recommend (!!) using the blocks using as I used now, as they ensure that the Streamreader will be arranged after use.

(Note: I haven’t tested the algorithm yet, I’m on Linux at the moment. Of course, I edit later if there are any problems)