将DataTable转换为列表< double>在R.NET [英] Convert DataTable to List<double> in R.NET

问题描述

我试图使用后台R和前端C＃使用R.NET连接器进行项目。
我想将DataTable转换为List，然后将其转换为NumericMatrix，因为R无法处理DataTable。

I'm trying to make a project using backend R and frontend C# using R.NET connector. I want to convert a DataTable to a List and then convert it to NumericMatrix, because R can't process DataTable.

但是当到达以下行时：

double r = Convert.ToDouble(row);

发生这个错误：

输入字符串格式不正确。

Input string was not in a correct format.

这是我的代码：

NumericMatrix matadata;
int nkolom = dataawal.Columns.Count;
if (nkolom > 1)
{
    for (int j = 1; j < nkolom; j++)
    {
        int kol = dataawal.Columns[j].Ordinal;
        List<double> s = new List<double>();
        for (int i = 0; i < dataawal.Rows.Count; i++)
        {
            String row = dataawal.Rows[i].ItemArray[kol].ToString();
            if (String.IsNullOrEmpty(row))
            {
                break;
            }
            else
            {
                double r = Convert.ToDouble(row); // NOTE Error comes here!
                s.Add(r);
            }
        }
        String nokol = Convert.ToString(j + 1);
        NumericVector v = engine.CreateNumericVector(s);
        engine.SetSymbol("dum", v);
        matadata = engine.Evaluate("matdt=matrix(cbind(matdt,dum),ncol=" + nokol + ")").AsNumericMatrix();
    }
}

推荐答案

，当您不确定表示双重值的字符串值的正确性时，您应该诉诸 double.TryParse 。如果字符串不能被识别为有效的双倍，则此方法不会引发异常，而是返回false，您可以跳过（或假定零）违规行。

Usually, when you are uncertain about the correctness of a string value representing a double value you should resort to double.TryParse. This method doesn't throw an exception if the string cannot be recognized as a valid double, instead it return false and you are able to skip (or assume zero) the offending row.

这样的事情

...
else
{
    double r;
    // if tryparse returns true then r has received the converted value
    if(double.TryParse(row, out r))
        s.Add(r);
}
...

然而，您可能会遇到其他问题，如值这是一个有效的双倍，但用当前语言环境设置无效的十进制格式表示。在这种情况下，您需要一种不同形式的double.TryParse。也接受实现 IFormatProvider 接口的类的实例。

However you could have other problems like a value that is a valid double but expressed with a decimal formatting not valid for your current locale settings. In this case you need a different form of double.TryParse. The one that accepts also an instance of a class that implements the IFormatProvider interface.

例如，假设你的要使用 it-IT 语言环境（其中逗号用十进制分隔整数部分）格式化，则应使用

For example, assuming that your wanna be doubles are formatted using the it-IT locale (where a comma delimits the integer part from the decimal) then you should use

CultureInfo ci = new CultureInfo("it-IT");

...
else
{
    double r;
    if(double.TryParse(row, NumberStyles.AllowDecimalPoint, ci, out r))
        s.Add(r);
}
...

这篇关于将DataTable转换为列表< double>在R.NET的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！