如何在R Markdown (pdf_document)中创建带有数学符号的表

Question

我正在用R Markdown写一篇论文，创建一个pdf文件。我想创建一个包含数学符号的表。下面是我的简单代码和一个表:

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```
## R Markdown
```{r  echo=FALSE}
library(knitr); library(kableExtra)
df <- data.frame(A=c("Hello!", 100, "$x^2+100$"), L=c(10, "World!", "100+250*1"))
knitr::kable(df, escape = FALSE, booktabs = TRUE,
caption = "An example[note]", 
col.names = c("Left", "Right")) %>%
add_indent(c(2, 3), level_of_indent = 1.5, all_cols = TRUE) %>%
add_footnote(c("Source: Book."), notation = "symbol")
```

因此，每次我编织文件时，都会出现相同的错误:

! Extra alignment tab has been changed to cr.
<recently read> endtemplate 

如果你能帮我改正这个错误，我将非常感激。

Answer 1

使用"使对齐错误更健壮:

library(xtable)
df <- data.frame(A=c("Hello!", 100, "$x^2+100$"), L=c(10, "World!", "100+250*1"))
table <- xtable(df, caption = "An example", label = "tab:example", col.names = c("Left", "Right"))
footnote <- list(pos = list(-1), command = c('\multicolumn{2}{r}{Source: Book.}'))
table <- add.to.row(table, footnote)
print(table, include.rownames = FALSE, floating = FALSE, hline.after = c(-1))

如果它不工作，试试这个:

library(xtable)
# your dataframe
df <- data.frame(A=c("Hello!", 100, "$x^2+100$"), L=c(10, "World!", "100+250*1"))
# Create the object
table <- xtable(df, caption = "An example", label = "tab:example", col.names = c("Left", "Right"))
# Print what you need
print(table, include.rownames = FALSE, floating = FALSE, hline.after = c(-1), footnote = 'Source: Book.')