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POHow to use acast (reshape2) within a function in R?
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copied!<p>I tried to use <code>acast</code> from <code>reshape2</code> within a self written function, but had the problem that acast did not find the data I send to it.</p> <p>Here is my data:</p> <pre><code>library("reshape2") x <- data.frame(1:3, rnorm(3), rnorm(3), rnorm(3)) colnames(x) <- c("id", "var1", "var2", "var3") y <-melt(x, id = "id", measure = c("var1", "var2", "var3")) </code></pre> <p><code>y</code> then looks like this:</p> <pre><code> id variable value 1 1 var1 0.1560812 2 2 var1 1.0343844 3 3 var1 -1.4157728 4 1 var2 0.8808935 5 2 var2 0.1719239 6 3 var2 0.6723758 7 1 var3 -0.7589631 8 2 var3 1.1325995 9 3 var3 -1.5744876 </code></pre> <p>now I can cast it back via <code>acast</code>:</p> <pre><code>> acast(y,y[,1] ~ y[,2]) var1 var2 var3 1 0.1560812 0.8808935 -0.7589631 2 1.0343844 0.1719239 1.1325995 3 -1.4157728 0.6723758 -1.5744876 </code></pre> <p>However, when writing a small wrapper for <code>acast</code> that should do the same, i get a stupid error messages:</p> <pre><code>wrap.acast <- function(dat, v1 = 1, v2 = 2) { out <- acast(dat, dat[,v1] ~ dat[,v2]) return(out) } wrap.acast(y) Error in eval(expr, envir, enclos) : object 'dat' not found </code></pre> <p>The problem is obviously related to something like environments and global/local variables. As it gives other error messages after declaring <code>dat</code> in the global environment (i.e., <code>v1</code> and <code>v2</code> not found as long as they aren't global).</p> <p><strong>I would like to use resahpe (especially acast) within a function without the necessity of declaring the variables outside the function. What is the trick?</strong></p> <p>Thanks.</p>

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