Array char char Array Console File.ReadAllText int Array Loop, String Chars

Letter frequencies

English text contains some letters more than others—for example, the lowercase "e" is often the most common. It is possible to compute a table of letter frequencies.

We can perform letter frequency analysis with a method in the C# language. This may be part of a project or required for simple textual analysis.

Example

The first part of the solution is declaring an array to store the frequencies. The char type is 2 bytes, which means it contains 65535 elements to store.

Part 1 We use the new char syntax and initialize the array size to char.MaxValue, which is a constant value defined in the .NET Framework.

Part 2 We read in the file. File.ReadAllText() efficiently reads the file and places its contents into a string.

Next We add up frequencies by iterating over each letter, and casting it to an int. We increment each "slot" for the letters we find.

Finally We display all letter or digit characters we found. The Console.WriteLine statement actually prints the results to the screen.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        // Array to store frequencies.
        int[] c = new int[(int)char.MaxValue];

        // Read entire text file.
        string s = File.ReadAllText("text.txt");

        // Iterate over each character.
        foreach (char t in s)
        {
            // Increment table.
            c[(int)t]++;
        }

        // Write all letters found.
        for (int i = 0; i < (int)char.MaxValue; i++)
        {
            if (c[i] > 0 && char.IsLetterOrDigit((char)i))
            {
                Console.WriteLine("Letter: {0}  Frequency: {1}", (char)i, c[i]);
            }
        }
    }
}aaaa
bbbbb
aaaa
bbbbb
aaaa bbbbb
CCcc
xx
y y y y y
ZLetter: C  Frequency: 2
Letter: Z  Frequency: 1
Letter: a  Frequency: 12
Letter: b  Frequency: 15
Letter: c  Frequency: 2
Letter: x  Frequency: 2
Letter: y  Frequency: 5

Some notes

Most important in the solution is how the array is declared and the constants are used. An array can be used to record counts.

Info The sections in the code show the input file, and the frequency counts, so we can easily see the method is correct.

We counted the letter frequencies in a string or file. This is handy code to have for text-based processing. It can be used to determine if a string is likely English or not.