Histograms in C# QuickStart Sample

Illustrates how to create histograms using the Histogram class in the Numerics.NET.DataAnalysis namespace in C#.

View this sample in: Visual Basic F# IronPython

using System;

using Numerics.NET.DataAnalysis;
using Numerics.NET;
using Index = Numerics.NET.DataAnalysis.Index;

namespace Numerics.NET.QuickStart.CSharp
{
    /// <summary>
    /// Illustrates the use of the Histogram class. 
    /// </summary>
    class Histograms
    {
        static void Main(string[] args)
        {
            // The license is verified at runtime. We're using
            // a 30 day trial key here. For more information, see
            //     https://numerics.net/trial-key
            Numerics.NET.License.Verify("64542-18980-57619-62268");

            // Histograms are used to summarize the distribution of data.
            // This QuickStart sample creates a histogram from data 
            // in a variety of ways.

            // We use the test scores of students on a hypothetical national test.
            // First we create a NumericalVariable that holds the test scores.
            var group1Results = Vector.Create(
                62, 77, 61, 94, 75, 82, 86, 83, 64, 84,
                68, 82, 72, 71, 85, 66, 61, 79, 81, 73);

            // We can create a histogram with evenly spaced bins 
            // by specifying the lower bound, the upper bound, 
            // and the number of bins:
            var histogram1 = Histogram.CreateEmpty(50, 100, 5);
            
            // We can also provide the bounds explicitly:
            int[] bounds = new int[] {50, 62, 74, 88, 100};
            var histogram2 = Histogram.CreateEmpty(bounds);

            // Or we can first create an Index object
            var index = Index.CreateBins(bounds);
            var histogram3 = Histogram.CreateEmpty(index);

            // To tally the results, we simply call the Tabulate method.
            // The data can be supplied as a vector:
            histogram1.Tabulate(group1Results);
            // or simply as any enumerable, including an array:
            histogram2.Tabulate(group1Results.ToArray());

            // You can add multiple data sets to the same histogram:
            histogram2.Tabulate(new int[] {74, 68, 89});
            // Or you can add individual data points using the Increment method.
            // This will increment the count of the bin that contains 
            // the specified value:
            histogram2.Increment(83);
            histogram2.Increment(78);

            // Histograms are just vectors, so the SetToZero method 
            // clears all the data:
            histogram2.SetToZero();

            // The Bins property returns an index of bins:
            var bins = histogram1.Bins;
            // The Length property returns the total number of bins:
            Console.WriteLine($"# bins: {bins.Length}");
            // For binned histograms, the bins are of type Interval<T>:
            Interval<int> bin = bins[2];
            // Interval structures have a lower bound, an upper bound:
            Console.WriteLine($"Bin 2 has lower bound {bin.LowerBound}.");
            Console.WriteLine($"Bin 2 has upper bound {bin.UpperBound}.");
            // You can get the value at a specific bin using the Get method:
            Console.WriteLine($"Bin 2 has value {histogram1.Get(bin)}.");

            // The histogram's FindBin method returns the Histogram bin
            // that contains a specified value:
            bin = histogram1.FindBin(83);
            Console.WriteLine($"83 is in bin {bin}");

            // You can use the BinsAndValues property to iterate through all the bins
            // in a for-each loop:
            foreach(var pair in histogram1.BinsAndValues)
                Console.WriteLine("Bin {0}: {1}", pair.Key, pair.Value);

            // You can also create histograms for categorical data:
            var success = Vector.CreateCategorical(
                new bool[] { true, false, true, true, false });
            var histogram4 = success.CreateHistogram();
            // Bins for categorical histograms are just the categories:
            var successes = histogram4.Get(true);
            Console.WriteLine(successes);

            Console.Write("Press any key to exit.");
            Console.ReadLine();
        }
    }
}