ClusterCollection doesn't implement IEnumerable properly (runtime error)

[pengowray]

Can ClusterCollection be fixed so IEnumerable works as expected?

When you have a cluster collection, e.g.
var clusters = new KMeans(3).Learn(observations);

and you want to iterate through them like this:

foreach (var cluster in clusters) { 
    // ... 
}

You receive the following error:

 Exception: System.InvalidCastException: Unable to cast object of type 'SZArrayEnumerator' to type 'System.Collections.Generic.IEnumerator`1[Accord.MachineLearning.KMeansClusterCollection+KMeansCluster]'.

Instead you need to use an old school for loop:

for (int i = 0; i < clusters.Count; i++) {
     var cluster = clusters[i];
     // ...
}

Can this be fixed?

---

Test code:

using Accord.MachineLearning;
using System;

// ...

double[][] observations =
{
    new double[] { -5, -2, -1 },
    new double[] { -5, -5, -6 },
    new double[] {  2,  1,  1 },
    new double[] {  1,  1,  2 },
    new double[] {  1,  2,  2 },
    new double[] {  3,  1,  2 },
    new double[] { 11,  5,  4 },
    new double[] { 15,  5,  6 },
    new double[] { 10,  5,  6 },
};

KMeans kmeans = new KMeans(3);
var clusters = kmeans.Learn(observations);

// OK
for (int i = 0; i < clusters.Count; i++) {
    var cluster = clusters[i];
    Console.WriteLine("Cluster {0}: {1:0.00}%", cluster.Index, cluster.Proportion);
}

// ERROR
foreach (var cluster in clusters) {
    Console.WriteLine("Cluster {0}: {1:0.00}%", cluster.Index, cluster.Proportion);
}

[cesarsouza]

Thanks for opening the issue! I have just committed a fix to the development branch.

[pengowray]

Excellent! Thanks for the fast response.

[cesarsouza]

Integrated in release 3.4.0.