knitr kable 和“*”

knitr kable and "*"

我正在尝试生成一个 table 并在单元格中将“*”作为值:

---
title: "Untitled"
author: "James Durant"
date: "November 7, 2017"
output: pdf_document
---

```{r arthmatic, echo=FALSE}
library(knitr)
dfx <- data.frame(
  Operator = c("+", "-", "*", "/", "^", "**", "%%", "%/%"),
  Operation = c("addition", "subtraction", "multiplication", 
                "division", "exponentiation", "exponentiation",
                "modulus", "integer division")
  )
kable(dfx, escape = FALSE)
```

但是*和**没有出现在table中:

有什么想法吗?

将每个 * 替换为 \text{*}\textasteriskcentered