public static SentimentAnalysisData AnalyzeReview(ReviewData data)
{
SentimentAnalysisData result = new SentimentAnalysisData {
Review = data
};
result.SentimentEvaluation = regression.Transform(CalculateProbabilities(data.reviewText));
return(result);
}
public void gh_937()
{
#region doc_learn_database
// Note: this example uses a System.Data.DataTable to represent input data,
// but note that this is not required. The data could have been represented
// as jagged double matrices (double[][]) directly.
// If you have to handle heterogeneus data in your application, such as user records
// in a database, this data is best represented within the framework using a .NET's
// DataTable object. In order to try to learn a classification or regression model
// using this datatable, first we will need to convert the table into a representation
// that the machine learning model can understand. Such representation is quite often,
// a matrix of doubles (double[][]).
var data = new DataTable("Customer Revenue Example");
data.Columns.Add("Day", "CustomerId", "Time (hour)", "Weather", "Buy");
data.Rows.Add("D1", 0, 8, "Sunny", true);
data.Rows.Add("D2", 1, 10, "Sunny", true);
data.Rows.Add("D3", 2, 10, "Rain", false);
data.Rows.Add("D4", 3, 16, "Rain", true);
data.Rows.Add("D5", 4, 15, "Rain", true);
data.Rows.Add("D6", 5, 20, "Rain", false);
data.Rows.Add("D7", 6, 12, "Cloudy", true);
data.Rows.Add("D8", 7, 12, "Sunny", false);
// One way to perform this conversion is by using a Codification filter. The Codification
// filter can take care of converting variables that actually denote symbols (i.e. the
// weather in the example above) into representations that make more sense given the assumption
// of a real vector-based classifier.
// Create a codification codebook
var codebook = new Codification()
{
{ "Weather", CodificationVariable.Categorical },
{ "Time (hour)", CodificationVariable.Continuous },
{ "Revenue", CodificationVariable.Continuous },
};
// Learn from the data
codebook.Learn(data);
// Now, we will use the codebook to transform the DataTable into double[][] vectors. Due
// the way the conversion works, we can end up with more columns in your output vectors
// than the ones started with. If you would like more details about what those columns
// represent, you can pass then as 'out' parameters in the methods that follow below.
string[] inputNames; // (note: if you do not want to run this example yourself, you
string outputName; // can see below the new variable names that will be generated)
// Now, we can translate our training data into integer symbols using our codebook:
double[][] inputs = codebook.Apply(data, "Weather", "Time (hour)").ToJagged(out inputNames);
double[] outputs = codebook.Apply(data, "Buy").ToVector(out outputName);
// (note: the Apply method transform a DataTable into another DataTable containing the codified
// variables. The ToJagged and ToVector methods are then used to transform those tables into
// double[][] matrices and double[] vectors, respectively.
// If we would like to learn a logistic regression model for this data, there are two possible
// ways depending on which aspect of the logistic regression we are interested the most. If we
// are interested in interpreting the logistic regression, performing hypothesis tests with the
// coefficients and performing an actual _logistic regression analysis_, then we can use the
// LogisticRegressionAnalysis class for this. If however we are only interested in using
// the learned model directly to predict new values for the dataset, then we could be using the
// LogisticRegression and IterativeReweightedLeastSquares classes directly instead.
// This example deals with the former case. For the later, please see the documentation page
// for the LogisticRegression class.
// We can create a new multiple linear analysis for the variables
var lra = new LogisticRegressionAnalysis()
{
// We can also inform the names of the new variables that have been created by the
// codification filter. Those can help in the visualizing the analysis once it is
// data-bound to a visual control such a Windows.Forms.DataGridView or WPF DataGrid:
Inputs = inputNames, // will be { "Weather: Sunny", "Weather: Rain, "Weather: Cloudy", "Time (hours)" }
Output = outputName // will be "Revenue"
};
// Compute the analysis and obtain the estimated regression
LogisticRegression regression = lra.Learn(inputs, outputs);
// And then predict the label using
double predicted = lra.Transform(inputs[0]); // result will be ~0.287
// Because we opted for doing a MultipleLinearRegressionAnalysis instead of a simple
// linear regression, we will have further information about the regression available:
int inputCount = lra.NumberOfInputs; // should be 4
int outputCount = lra.NumberOfOutputs; // should be 1
double logl = lra.LogLikelihood; // should be -4.6035570737785525
ChiSquareTest x2 = lra.ChiSquare; // should be 1.37789 (p=0.8480, non-significant)
double[] stdErr = lra.StandardErrors; // should be high except for the last value of 0.27122079214927985 (due small data)
double[] or = lra.OddsRatios; // should be 1.1116659950687609 for the last coefficient (related to time of day)
LogisticCoefficientCollection c = lra.Coefficients; // coefficient table (bind to a visual control for quick inspection)
double[][] h = lra.InformationMatrix; // should contain Fisher's information matrix for the problem
#endregion
Assert.AreEqual(0.28703150858677107, predicted, 1e-8);
Assert.AreEqual(4, inputCount, 1e-8);
Assert.AreEqual(1, outputCount, 1e-8);
Assert.AreEqual(-4.6035570737785525, logl, 1e-8);
Assert.IsTrue(new[] { 0.0019604927838235376, 88.043929817973222, 101.42211648160144, 2.1954970044905113E-07, 1.1116659950687609 }.IsEqual(or, 1e-4));
Assert.AreEqual(1.377897662970609, x2.Statistic, 1e-8);
Assert.AreEqual(0.84802726696077046, x2.PValue, 1e-8);
}
