绘图错误，使用 svm 时缺少公式 [英] Error in plot, formula missing when using svm

问题描述

我正在尝试绘制我的 svm 模型.

I am trying to plot my svm model.

library(foreign)
library(e1071)

x <- read.arff("contact-lenses.arff")
#alt: x <- read.arff("http://storm.cis.fordham.edu/~gweiss/data-mining/weka-data/contact-lenses.arff")
model <- svm(`contact-lenses` ~ . , data = x, type = "C-classification", kernel = "linear")

隐形眼镜arff是weka中内置的数据文件.

The contact lens arff is the inbuilt data file in weka.

但是，现在我在尝试绘制模型时遇到了错误.

However, now i run into an error trying to plot the model.

 plot(model, x)
Error in plot.svm(model, x) : missing formula.

推荐答案

问题是在您的模型中，您有多个协变量.plot() 仅在您的 data= 参数正好有三列(其中一列是响应)时才会自动运行.例如，在 ?plot.svm 帮助页面中，您可以调用

The problem is that in in your model, you have multiple covariates. The plot() will only run automatically if your data= argument has exactly three columns (one of which is a response). For example, in the ?plot.svm help page, you can call

data(cats, package = "MASS")
m1 <- svm(Sex~., data = cats)
plot(m1, cats)

因此，由于您只能在图上显示两个维度，因此当您有多个可供选择时，您需要指定要用于 x 和 y 的内容来自

So since you can only show two dimensions on a plot, you need to specify what you want to use for x and y when you have more than one to choose from

cplus<-cats
cplus$Oth<-rnorm(nrow(cplus))
m2 <- svm(Sex~., data = cplus)
plot(m2, cplus) #error
plot(m2, cplus, Bwt~Hwt) #Ok
plot(m2, cplus, Hwt~Oth) #Ok

这就是您收到缺少公式"错误的原因.

So that's why you're getting the "Missing Formula" error.

还有一个问题.plot.svm 只会沿着 x 和 y 轴绘制连续变量.隐形眼镜 data.frame 只有分类变量.据我所知，plot.svm 函数根本不支持这一点.您必须决定如何在自己的可视化中总结这些信息.

There is another catch as well. The plot.svm will only plot continuous variables along the x and y axes. The contact-lenses data.frame has only categorical variables. The plot.svm function simply does not support this as far as I can tell. You'll have to decide how you want to summarize that information in your own visualization.

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