Problem with mathematical expression and loop
On 3/31/2009 9:15 AM, Denis Aydin wrote:
Hi to all I use a loop to plot 9 different histograms of 9 different transformations of one dataset (x). I want to label the histograms with the mathematical expression of each transformation (e.g. x^3). For that I've prepared a vector with the labeling names for "expression".
> trans.expr <- c("x^3", "x^2", "x", "frac(1,x)", "frac(1,x^2)",
> "frac(1,x^3)", "sqrt(x)", "log(x)", "frac(1,sqrt(x))")
> for(i in 1:9){
>
> hist(x[i], main=expression(trans.expr[i]))
>
> }
But if I want to pass the names to "expression", it always prints "trans.expr[i]" instead of the mathematical expressions.
Don't use a character vector, use expressions from the beginning:
trans.expr <- expression(x^3, x^2, x, frac(1,x), frac(1,x^2),
frac(1,x^3), sqrt(x), log(x), frac(1,sqrt(x)))
for (i in 1:9) hist(x[i], main=trans.expr[i])
If you really need to use strings, then you need parse() to convert them
to expressions.
Duncan Murdoch
I also tried to use "noquote" to remove the quotes but it didn't work. Does anyone knows a solution to that problem? Any help is appreciated. Denis
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