R, Knitr, Rnw, beautiful scientific numbers

Question

I would like that all numbers generated by my knitr codes don´t look like an oldfashioned calculator.

Is there any option to get the numbers like the last one (with ·10 instead of e or E) ?

options(scipen=...) doesn't seem to have that option.

I've been searching information and I've found that it can be done directly in LaTex with the package siunitx, writing every number like this \num{1e-10}

But I'd like knitr did it automatically for all numbers, including those within tables.

PD: And how can I avoid that [1] when I print something?

PD2: Maybe something with gsub?

PD3:
I'm coming back to this problem. Imagine I don't define my own table but I get it from a regression and use xtable to produce it.

\documentclass{article}
\usepackage{siunitx}
\usepackage{booktabs}
\sisetup{     group-minimum-digits = {3},    group-separator = {,}, exponent-product = \cdot     }
\begin{document}

<<r, results='asis'>>=

library(xtable)
data(tli)
fm2 <- lm(tlimth ~ sex*ethnicty, data = tli)
xxx <- xtable(fm2)
print(xxx, booktabs = TRUE)

@
\end{document}

But it doesn't work well. What options should I use?

This is the result just with print

And this is the result with print+"booktabs=T"+my function beauty(). regards.

I don't know why it produces two tables instead of 1. And the numbers are not properly aligned. Anyway, I would like not to depend on my beauty() function but just use suintx, how can I do it?

Answer 1

---
output: pdf_document
---


```{r, results='asis'}
x <- 6.22e-21

cat(x)

cat(sfsmisc::pretty10exp(x, lab.type = 'latex')[[1]])
```

Answer 2

I prefer to leave the formatting to siunitx, but the pre-processing in R can get a bit fiddly,

---
output: 
  pdf_document: 
    keep_tex: yes
header-includes:
- \usepackage{siunitx}
- \usepackage{booktabs}
---

\sisetup{detect-all, tight-spacing=false, exponent-product = \cdot,
round-mode = figures,
round-precision = 3}

```{r, results='asis'}
as.sci_fy <- function(x) {class(x) <- c("sci_fy", class(x)); x}
format.sci_fy <-  function(x) sprintf("\\num{%e}", x)
print.sci_fy <- function(x) cat(format(x))


x <- 6.22e-21
as.sci_fy(x)

d <- data.frame(x=rnorm(10), y=rnorm(10), f=letters[1:10])
d <- lapply(d, function(c) if(is.numeric(c)) format(as.sci_fy(c)) else c)

library(xtable)
d <- xtable(data.frame(d, stringsAsFactors = FALSE))
 print(d, type="latex", align = c("l", "l", "l"),
        table.placement = "!htpb",
        floating.environment = "table",
        include.rownames=FALSE, 
       sanitize.text.function = function(x){x}, booktabs=TRUE)

```