Decimal separator and $$ notation

[cmmp]

Hi,

I'm using comma as a decimal separator: options(OutDec = ',').

I have this small formatting issue:

When I use \Sexpr{0.5} inline with text, the output 0,5 is nicely formatted.

However, if I have to use it inside a math expression, like $\alpha = \Sexpr{0.5}$, then the 0, 5 is output with an extra space after the comma. If I write $\alpha = \text{\Sexpr{0.5}}$ then it works ok.

is there another simpler (more elegant) workaround or a fix for this?

thanks!
Cássio

[yihui]

You can hack at the inline hook to add \text{} to numbers, e.g.

knit_hooks$set(inline = function(x) {
  if (is.numeric(x)) x = sprintf('\\text{%s}', knitr:::format_sci(x, 'latex'))
  knitr:::.inline.hook(x)
})

but in the non-math mode that will be problematic. However, you can continue hacking at it, e.g. let I(0.5) be 0,5, and a normal 0.5 be \text{0,5}. Check the class of the number by inherits(x, 'AsIs') and decide if you need \text{} or not.

[cmmp]

yeah, I'm not sure, maybe that's more fragile to corner cases than adding \text{} altogether. Reading this makes me think that maybe knitr could check if outdec is something other than '.', and then to use siunitx or numprint inside for numbers. But I'm not sure if this is too a corner case to handle in the package or not.

[yihui]

You can design an inline hook first, and I may accept a pull request after it works well for you. Frankly speaking, I was not even aware of the OutDec option in the past before you mentioned it to me.

[cmmp]

I have to think about this... what if x is an expression and not just a number? is the expression evaluated before the hook is called or after? e.g. \Sexpr{0.6*2} vs \Sexpr{1.2} or worse \Sexpr{paste('a = ', 1.2)}

[yihui]

The expression is always evaluated before being passed to the hook.

[cmmp]

Ok, I don't understand what you mean with

let I(0.5) be 0,5, and a normal 0.5 be \text{0,5}

and the need to check using inherits.

I also don't know why you said the hook you provided will be problematic outside a math environment. Could you clarify that?

I tried it and it works (in and out of math environments)... it adds \text{} always, but I could live with that.

Here's the example I created:

\documentclass[a4paper]{article}

\usepackage{amsmath}

\begin{document}

\title{Test}

\maketitle

<<>>=
options(OutDec = ',')
@

<<>>=
knit_hooks$set(inline = function(x) {
    if (is.numeric(x)) x = sprintf('\\text{%s}', knitr:::format_sci(x, 'latex'))
      knitr:::.inline.hook(x)
})
@ 

\section{Test}

This is the first test. abc \Sexpr{0.6} def

another test $a = \Sexpr{0.6}$.

\end{document}

at least for these simple cases it works.

An issue I see is that \text{} is provided by amsmath, so for this to work knitr would have to include that package. Not a problem by me, but maybe someone for some reason may not want to include that package.

[yihui]

sorry I thought \text{} is for the math mode only like ^ and _

amsmath does not matter because you use it only when OutDec is not ., and I guess most R users do not use other characters, so this will not actually affect them at all

for I(0.5), I mean something like x = if (inherits(x, 'AsIs')) x else sprintf('\\text{%s}', x)

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