wpf对excel中的二维浮点数据进行拟合，输出函数方程和函数曲线图，写出xaml代码和后端代码，列出需要的nuget库

需要的 NuGet 库：MathNet.Numerics、ExcelDataReader和OxyPlot.Wpf。

下面是 XAML 代码：

<Window x:Class="ExcelFitting.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:oxy="http://oxyplot.org/wpf"
        Title="Excel Fitting" Height="450" Width="800">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <StackPanel Grid.Row="0" Orientation="Horizontal" HorizontalAlignment="Center" Margin="0,10">
            <Button Content="Open Excel File" Margin="10" Click="OpenExcelFile_Click"/>
            <Button Content="Fit Data" Margin="10" Click="FitData_Click"/>
        </StackPanel>
        <oxy:Plot Grid.Row="1" Margin="10" Model="{Binding PlotModel}"/>
    </Grid>
</Window>

下面是后端代码：

using System;
using System.Collections.Generic;
using System.Data;
using System.IO;
using System.Linq;
using System.Windows;
using ExcelDataReader;
using MathNet.Numerics.LinearRegression;
using OxyPlot;
using OxyPlot.Axes;
using OxyPlot.Series;

namespace ExcelFitting
{
    public partial class MainWindow : Window
    {
        private DataTable data;
        private List<double> xValues;
        private List<double> yValues;

        public PlotModel PlotModel { get; set; }

        public MainWindow()
        {
            InitializeComponent();

            PlotModel = new PlotModel
            {
                Axes =
                {
                    new LinearAxis { Position = AxisPosition.Bottom },
                    new LinearAxis { Position = AxisPosition.Left },
                }
            };
            DataContext = this;
        }

        private void OpenExcelFile_Click(object sender, RoutedEventArgs e)
        {
            var dialog = new Microsoft.Win32.OpenFileDialog
            {
                DefaultExt = ".xlsx",
                Filter = "Excel Files (*.xlsx)|*.xlsx|All Files (*.*)|*.*"
            };
            if (dialog.ShowDialog() == true)
            {
                var stream = File.Open(dialog.FileName, FileMode.Open, FileAccess.Read);
                var reader = ExcelReaderFactory.CreateReader(stream);
                data = reader.AsDataSet().Tables[0];
                xValues = data.Rows.Cast<DataRow>().Select(row => Convert.ToDouble(row[0])).ToList();
                yValues = data.Rows.Cast<DataRow>().Select(row => Convert.ToDouble(row[1])).ToList();
            }
        }

        private void FitData_Click(object sender, RoutedEventArgs e)
        {
            if (xValues == null || yValues == null)
            {
                MessageBox.Show("Please select an Excel file first!");
                return;
            }

            var coefficients = Fit.Line(xValues.ToArray(), yValues.ToArray());
            var a = coefficients.Item2;
            var b = coefficients.Item1;

            var series = new LineSeries
            {
                Title = $"y = {a:F2}x + {b:F2}",
                MarkerType = MarkerType.Circle,
                MarkerSize = 4,
                MarkerStroke = OxyColors.White
            };
            for (var x = xValues.Min(); x <= xValues.Max(); x += 0.1)
            {
                var y = a * x + b;
                series.Points.Add(new DataPoint(x, y));
            }
            PlotModel.Series.Clear();
            PlotModel.Series.Add(series);
            PlotModel.InvalidatePlot(true);
        }
    }
}

在上面的代码中，`OpenExcelFile_Click` 方法用于打开 Excel 文件，获取数据并将其存储在 `xValues` 和 `yValues` 中。`FitData_Click` 方法对这些数据进行拟合，并将拟合结果绘制在 `PlotModel` 上。

注意，在 `FitData_Click` 方法中，我们使用 `Fit.Line` 方法进行线性拟合。如果需要进行其他类型的拟合，可以使用 `Fit.Polynomial` 或 `Fit.LinearCombination` 等方法。