Convert R yacas equation to LaTeX without solving it

Question

I want to show step-by-step calculations that were made using 'TeXForm' in Ryacas.
To do that I must be able to obtain LaTeX from given equation. Issue is that yacas automatically solves them before converting to LaTeX form. If I try to apply 'TeXForm' on equation, I get simplified version of it. For example:

exp1<-'D(x)Sin(x^2+y^2)+D(y)Sin(x^2+y^2)'
TeXForm(exp1)

I got:

"$2 x \cos \left( x ^{2} + y ^{2}\right)  + 2 y \cos \left( x ^{2} + y ^{2}\right) $";

I tried to get non-simplified version:

 yacas('TeXForm(exp1)')

I got:

"$\mathrm{ exp1 }$";

I also tried:

yacas('D(x)Sin(x^2+y^2)+D(y)Sin(x^2+y^2)')

It didn`t work either.
How to get non-simplified LaTeX formula with all derivatives?

score 1 · Answer 1 · answered Sep 20 '18 at 11:54

To prevent yacas to evaluate your expression, you can wrap your expression with Hold().

E.g: You have an expression "Limit(x,0) Sqrt(x) * Sin(1/x)", and you want yacas to parse this and convert it to the LaTeX format, without evaluating the expression.

Expand your expression like this:

s <- "Limit(x,0) Sqrt(x) * Sin(1/x)" 
expanded_yacas_charstr <- paste("Hold(", s, ") == ", s, sep = "")

I made a function to use this in Rmarkdown documents, returning the input function along with its result, as a combined LaTeX result. This might be useful to you:

```{r, results="asis", echo=FALSE}

  kalk <- function(s) {
  library("Ryacas")

  # Expand yacas expression
  # e.g. 
  #       Limit(x,0) Sqrt(x) 
  # is expanded to 
  #       Hold("Limit(x,0) Sqrt(x) == )" Limit(x,0) Sqrt(x)
  #
  # This prevents yacas to evaluate the text inside Hold()

  expanded_yacas_charstr <- paste("Hold(", s, ") == ", s, sep = "")

  s <- as.character(yacas(verbose=false,
                          TeXForm(expanded_yacas_charstr),
                          retclass = "unquote"))

  return(paste("$$ ", substr(s, 2, nchar(s)), "$", sep = ""))
}

# use cat() to make sure "[1]"" output is removed
cat(kalk("Limit(x,0) Sqrt(x) * Sin(1/x)"))
```

I just loaded `Ryacas` and there is no longer a function `yacas` . Is `yac` the same thing? — Carl Witthoft, Jan 24 '20 at 18:32
@CarlWitthoft https://mikl.dk/post/2019-06-26-ryacas-update/ There has been a large rewrite of `Ryacas` - read the documentation on the new approach. — haakonstorm, Feb 17 '20 at 18:17

score 0 · Accepted Answer · answered Aug 13 '15 at 09:58

0

I found that TeXForm(deparse(x^2+x^2)) gives right result, but that doesn't work with derivatives.
For derivatives: TeXForm(substitute("D(x) sin(x+y)")).

answered Aug 13 '15 at 09:58

Alex Alex

235
2
14

score 0 · Answer 3 · edited Jan 28 '20 at 22:23

0

Some functions are ok :

for example :

TeXForm(Hold(Integrate(a) (a^2+5)) )

give :

$\int \left( a ^{2} + 5\right)  da$

but not all functions... this one don't match :

TeXForm(substitute("D(x) sin(x+y)"))

but even :

TeXForm(Hold(D(x)Sin(x^2+y^2)+D(y)Sin(x^2+y^2)))

give :

$2 x \cos \left( x ^{2} + y ^{2}\right)  + \frac{\partial}{\partial x}\left( 2 y \cos \left( x ^{2} + y ^{2}\right) \right) $

It's in the doc : "https://yacas.readthedocs.io/en/latest/reference_manual/controlflow.html#Hold"

edited Jan 28 '20 at 22:23

mcarton

27,633
5
85
95

answered Jan 28 '20 at 17:14

MDAions

1

This answer doesn't seem to give a complete explanation. Try being more detailed in what you describe. Linking to documentation is not helpful unless it is to cite sources. You should extract the important aspects of the documentation you linked and translate it to something that applies to OP's situation. – RagingRoosevelt Jan 28 '20 at 19:12

Convert R yacas equation to LaTeX without solving it

3 Answers3