Try this:
> a <- 1
> b <- 2
> mat <- matrix(c("a", "a*b", "a+b", "b"), 2)
> mat
[,1] [,2]
[1,] "a" "a+b"
[2,] "a*b" "b"
> matrix(sapply(mat, function(x) eval(parse(text = x))), nrow(mat))
[,1] [,2]
[1,] 1 3
[2,] 2 2
On Nov 30, 2007 10:06 AM, BOISSON, Pascal <[EMAIL PROTECTED]> wrote:
> Dear R_Users,
>
> I am confronted to a technical issue that I wouldn't even know how to start
> to handle and where to look at. It is about data manipulation in a dataframe
> and value substitution
> Imagine I have a matrix describing a set of chemical equations.
> Colnames are Components names and Rownames are Reaction names
>
> Each cell in that matrix corresponds to the stoechiometric coefficient to the
> pair (Reaction, Component). It would be easy to deal with this if these cells
> where filled with numbers (int or real) but often, it refers to some
> parameters name or even to formulae.
>
> I'd like to transform these formulae into their calculated values.
> eg:
> if I have existing R objects :
> f_ox <- 0.2
> f_inox <- 0.5
>
> and in my matrix :
> cell (Oxydation, substrate) = f_ox*(1-f_inox)
>
> I want to replace f_ox*(1-f_inox) by 0.1
>
> Further more, I can not manage to understand the formula type, which I guess
> would correspond to the kind of things I am dealing with.
>
> Would you have any clue or insights on this?
>
> Pascal Boisson
>
> Assainissement - Traitement Biologique
> Veolia Environnement - Centre de Recherche sur l'Eau
> Anjou Recherche
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