因素，级别，R语法说明 [英] Factors, levels, R syntax explanation

问题描述

我对如何使用和操纵因素有一个普遍的问题.在我的工作中，R经常将某些内容强制转换为一个因子，因为R不允许在矩阵中使用不同的模式，但实际上，我希望这些列保持数字形式.

I have a generic question of how to use and manipulate factors. In my work, R often coerces something into a factor because R does not allow different modes in a matrix, but in actuality I would prefer those columns to remain numeric.

在处理这些因素时，我注意到:

When working with such factors I noticed:

• 在不同的列中有两个相似的因子(例如1到5之间的所有值)时，将第一列因子强制为as.numeric()即可.通过as.numeric强制第二个，第三个或第四个总是向每个因数"加1.为什么?

• When you have two similar factors (e.g all values between 1 and 5) in different columns, coercing the first column factor to a number by as.numeric() works fine. Coercing the second, third or fourth via as.numeric always adds 1 to every "factor". Why?

两者之间似乎有所不同

go$V4 <- as.double(go$V4)

AND

go[,4] <- as.numeric(levels(go[,4]))[go[,4]]

假设as.double和as.numeric确实基本相同，区别在其他地方，但我不明白.

Assuming as.double and as.numeric are indeed largely identical, the difference is somewhere else but I don't get it.

任何语法专家吗?

推荐答案

关于强制将矩阵要求的b/c因子分解的说法是错误的. (R矩阵无法保存因子变量.)也许您正在考虑一个data.frame.正如R FAQ所说，您需要使用:

The statement about coercing to factor b/c of matrix requirements is simply wrong. (R matrices are incapable of holding factor variables.) Perhaps you are thinking of a data.frame. As the R FAQ says you need to use:

go$V4 <- as.numeric(as. character(go$V4))

如果将数字矢量(用c())连接到任何字符矢量，它将立即强制为字符"模式.如果文本字段中的一列中包含非数字字符，则输入时也会发生同样的情况.

If a numeric vector is concatenated (with c()) to any character vector, it is immediately coerced to "character" mode. If a column in a text field has non-numeric characters in it, the same thing happens on input.

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