Sunday, April 15, 2018

C#: A Linear Regression example with the NelderMead solver from Microsoft Solver Foundation (MSF)


Given that you installed the Microsoft Solver Foundation (msdn.microsoft.com)
and referenced the MSF dll (Microsoft.Solver.Foundation.dll) in your VisualStudio Project here is a simple code to test the NonLinear solver (aka NelderMead solver)  that ships with the library.

I hope Microsoft will revive this nice library in the future (at the moment the project is abandoned :( )

// here is the code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.SolverFoundation.Common;
using Microsoft.SolverFoundation.Services;
using Microsoft.SolverFoundation.Solvers;

namespace LinearRegression_with_MSF
{
    class Program
    {

    // We want to get a this line's coefficients back: y = 11.22*x + 77.99
   
        static double[] xData = new double[] { 0, 1, 2, 3, 4, 5, 6, 7 };
        static double[] yData = new double[] { 0 * 11.22 + 77.99, 1 * 11.22 + 77.99, 2 * 11.22 + 77.99, 3 * 11.22 + 77.99, 4 * 11.22 + 77.99, 5 * 11.22 + 77.99, 6 * 11.22 + 77.99, 7 * 11.22 + 77.99 };


        static void Main(string[] args)
        {

            LinearRegression_with_NelderMead_Solver();

            Console.ReadKey();
        }



        private static void LinearRegression_with_NelderMead_Solver()
        {
            // initial values for the two paramenters
            double[] pInitial = new double[] { 1, 1 };
           
            // lower and upper limits for the two paramenters           
            double[] pLower = new double[] { -100, -100 };
            double[] pUpper = new double[] { 100, 100 };

            var solution = NelderMeadSolver.Solve(SumOfSquares, pInitial, pLower, pUpper);

            Console.WriteLine(solution.Result);
            Console.WriteLine("solution = {0}", solution.GetSolutionValue(0));
            Console.WriteLine("x = {0}", solution.GetValue(1));
            Console.WriteLine("y = {0}", solution.GetValue(2));
        }


        private static double SumOfSquares(double[] p)
        {
            double q = p[0];
            double m = p[1];

            double dSumOfSquares = 0;

            for (int i = 0; i < xData.Length; ++i)
            {
                dSumOfSquares += Math.Pow(yData[i] - m * xData[i] - q, 2);
            }

            return dSumOfSquares;
        }
    }

}

Monday, March 12, 2018

Entity Framework: Model successfully updated but changes are not available in code

I lost quite some time on this annoying issue that sometimes affects my VisualStudio 2015 with the Devart Oracle Driver for using Entity Framework.

My changes in the database (for example a modification of a view) were reflected ONLY in the entity framework model (after selecting the usual Update Model from Database...) but the modified classes WERE NOT available in the code!

The solution is very simple: "Run Custom Tool"

Select your model file (the one with extension with .edml), right click an choose "Run Custom Tool".

Now the changes to your database are available in your code too.

Source:

https://blog.jongallant.com/2012/08/entity-framework-manual-update/

Sunday, February 18, 2018

Where is java on macOS?

Open the terminal and execute the following command:


/usr/libexec/java_home -v 1.7


It will locate the files corresponding to the provided java version.
 
Here the link for Java6 from Apple (useful is you want to install Matlab):

https://support.apple.com/kb/dl1572?locale=en_US

Thursday, January 25, 2018

Excel-Files take way too to open [Windows 10 issue on Dell]

This is not strictly speaking a programming issue, but definitely something quite annoying.
On my Windows 10 on my DELL  OptiPlex,  opening an excel file used to take about 30 seconds! It didn't matter if the file was on a local or network folder!
The issue was, in my case, related to the Audio Driver. Yes! An issue with Excel was related to the Realtek Audio Driver!

Anyway, here is the Dell's post:

http://www.dell.com/support/article/de/de/debsdt1/sln306701/slow-performance-issues-in-excel-when-opening-saved-files?lang=en

Solution:

Find your Computer Version in http://www.dell.com/support/drivers/home and update your Audio Driver

Monday, December 11, 2017

C#: Import excel file as dataset using OLEDB

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Data;
using System.Data.OleDb;
using System.Linq;
using System.Text;

namespace cltStammdatenImporterGUI
{
    public class ExcelFile
    {

        public static DataSet DataSetFromExcelFile(string sExcelFilename, string sExcelRange = "")
        {
            DataSet ds = new DataSet();

            string connectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + sExcelFilename + ";Extended Properties='Excel 12.0 XML;HDR=NO;IMEX=1;';";

            using (OleDbConnection conn = new OleDbConnection(connectionString))
            {
                conn.Open();
                OleDbCommand cmd = new OleDbCommand();
                cmd.Connection = conn;

                // Get all Sheets in Excel File
                DataTable dtSheet = conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);

                // Loop through all Sheets to get data
                foreach (DataRow dr in dtSheet.Rows)
                {
                    string sheetName = dr["TABLE_NAME"].ToString();

                    if (!sheetName.EndsWith("$"))
                        continue;

                    // Get all rows from the Sheet. sExcelRange must be in the form A1:C10 or sim or just empty
                    cmd.CommandText = "SELECT * FROM [" + sheetName + sExcelRange + "]";

                    DataTable dt = new DataTable();
                    dt.TableName = sheetName;

                    OleDbDataAdapter da = new OleDbDataAdapter(cmd);
                    da.Fill(dt);

                    ds.Tables.Add(dt);
                }

                cmd = null;
                conn.Close();
            }

            return ds;
        }
}
}

Tuesday, December 5, 2017

[C#] How to fix the "Microsoft.ACE.OLEDB.12.0 provider is not registered on the local machine" error

If you are trying to read an excel file in C# and you get this error:

The 'Microsoft.ACE.OLEDB.12.0' provider is not registered on the local machine.

You need to install "Microsoft Access Database Engine 2010 Redistributable" that is available at the Microsoft's website:


https://www.microsoft.com/en-in/download/details.aspx?id=13255

Wednesday, November 22, 2017

C# : How Convert doubles to strings ALWAYS with dots instead of commas

To convert a double to string ALWAYS with dots instead of commas (as it is used in some languages like Italian or German) you need to use an overloaded version of the ToString() method.



Example:

double dVal = 77.55;
string sVal = dVal.ToString(System.Globalization.CultureInfo.InvariantCulture);
// sVal will be  always "77.55"


or if you use System.Globalization


using System.Globalization;

double dVal = 77.55;
string sVal = dVal.ToString(CultureInfo.InvariantCulture);