如何在R中为C5.0软件包设置成本矩阵？ [英] How to set costs matrix for C5.0 Package in R?

问题描述

我在网上搜索了很多内容，但是没有找到R中C5.0函数的'costs'参数的有用描述。在C5.0 R手册中，它只是说成本矩阵矩阵应具有C列和行，其中C是类级别数。它不会告诉我行还是列是模型的预测结果。

I have googled much in the web, but don't find any useful description for the 'costs' parameter for C5.0 function in R. From the C5.0 R manual book, it just says "a matrix of costs associated with the possible errors. The matrix should have C columns and rows where C is the number of class levels". It does not tell me whether the row or the column is the predicated result by the model.

任何人都可以

推荐答案

以下是C5.0（版本0.1.0-15）的帮助页面中的报价：

Here is a quote from the help page of C5.0 (version 0.1.0-15):

成本矩阵应为CxC，其中C为类别数。
对角元素将被忽略。列应对应于真实的
类，而行则是预测的类。例如，如果C = 3，且
类别为红色，蓝色和绿色（按此顺序），则矩阵（2,3）
元素中的值为5表示预测的成本
绿色示例为蓝色，是蓝色值（通常是一个值）的五倍。

The cost matrix should by CxC, where C is the number of classes. Diagonal elements are ignored. Columns should correspond to the true classes and rows are the predicted classes. For example, if C = 3 with classes Red, Blue and Green (in that order), a value of 5 in the (2,3) element of the matrix would indicate that the cost of predicting a Green sample as Blue is five times the usual value (of one).

按照帮助页面中的示例进行操作，这将是一个成本矩阵：

Following the example in the help page, this would be a cost matrix:

cost.matrix <- matrix(c(
  NA, 2, 4,
  3, NA, 5,
  7, 1, NA

), 3, 3, byrow=TRUE)

rownames(cost.matrix) <- colnames(cost.matrix) <- c("Red", "Blue", "Green")

cost.matrix

      Red Blue Green
Red    NA    2     4
Blue    3   NA     5
Green   7    1    NA

这意味着：

• 将红色样本预测为蓝色是通常值的3倍（一个）


• 将红色样本预测为绿色，是通常值的7倍


• 预测蓝色样本样本为红色是正常值的2倍


• 预测蓝色样本为绿色是1倍常规值


• 预测绿色样本为红色为正常值正常值的4倍


• 将绿色样本预测为蓝色是通常值的5倍

• Predicting a red sample as blue is 3 times the value as the usual value (one)
• Predicting a red sample as green is 7 times the value as the usual
• Predicting a blue sample as red is 2 times the ususal value
• Predicting a blue sample as green is 1 times the ususal value
• Predicting a green sample as red is 4 times the ususal value
• Predicting a green sample as blue is 5 times the usual value

这篇关于如何在R中为C5.0软件包设置成本矩阵？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！