Laura Holt lauraholt_983 at hotmail.com writes:
. I would like to generate a vector/variable name from within a loop to be
. passed to a table
. function.
.
. This is what I have so far:
. assign(p1,paste(raw3.df$,rw2$V1[3],sep=))
. p1
. [1] raw3.df$CITIZEN
.
. Essentially, I want to use the raw3.df$CITIZEN along with another value to
. generate a table.
You can use eval and parse to parse and execute
arbitrary R commands that you construct from strings. The exec
function below is a one statement convenience function
that pastes its arguments together and executes them this way in
its parent's environment. (Sometimes when one gets complex
requirements like this if one backs up a bit one discovers
that the requirements can be simplified and you might
consider whether that is the case here in which case you
might be able to disregard all this.)
R ### create some test data ###
R data(iris)
R irish - head(iris)
R irish
Sepal.Length Sepal.Width Petal.Length Petal.Width Species
1 5.1 3.5 1.4 0.2 setosa
2 4.9 3.0 1.4 0.2 setosa
3 4.7 3.2 1.3 0.2 setosa
4 4.6 3.1 1.5 0.2 setosa
5 5.0 3.6 1.4 0.2 setosa
6 5.4 3.9 1.7 0.4 setosa
R ### this is the actual processing ###
R exec - function(...) eval.parent(parse(text = paste(..., collapse = )))
R exec(irish$Sepal.Length, -, irish$Sepal.Length, +1)
R irish
Sepal.Length Sepal.Width Petal.Length Petal.Width Species
1 6.1 3.5 1.4 0.2 setosa
2 5.9 3.0 1.4 0.2 setosa
3 5.7 3.2 1.3 0.2 setosa
4 5.6 3.1 1.5 0.2 setosa
5 6.0 3.6 1.4 0.2 setosa
6 6.4 3.9 1.7 0.4 setosa
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