varname <- c("a", "b", "d")you can do
get(varname[1]) + 2for a + 2
or
assign(varname[1], 2 + 2)for a <- 2 + 2
or
eval(substitute(lm(y ~ x + variable), list(variable = as.name(varname[1]))for lm(y ~ x + a)
At least in the first two cases it is often easier to just use a list, and then you can easily index it by name
vars <- list(a = 1:10, b = rnorm(100), d = LETTERS) vars[["a"]]without any of this messing about.
how can I assign NULL to a variable and have it evaluated properly
RispondiEliminafor example I want to automate the following two commands
qplot(x,data=myData,weight=depth)
qplot(x,data=myData,weight=NULL)
but use a myWeight variable each time
Is the following what you are looking for?
RispondiEliminamyWeight <- c(12,"NULL")
qplot(x, data=myData, weight=myWeight[1])
qplot(x, data=myData, weight=myWeight[2])
HTH