How to use variable labels in R?

问题

I have a function that takes input as the column name of dataframe as columnname~1.

The dataframe consists of about 50 columns in which I want to repeat the process, I can

use a for loop to generate column name as a character which unfortunately the function does

not recognize. The difference is just M1~1 (works) vs "M1"~1

Any suggestions are welcome

回答1:

Try:

as.formula(paste("M1","1",sep="~"))

回答2:

Use the "[[ function?

datafrm[[M1]] ~ 1

That function will interpret the character value and convert it to a language value. Or you could use the do.call function. Best answers will be forthcoming if we have specifics of the dataframe and the function.

回答3:

Or as an alternative to paste you can use sprintf:

variablename = "M1"
as.formula(sprintf("%s ~ 1", variablename))

回答4:

You can also use this:

substitute(columnname~1,list(columnname=as.name("M1")))

EDIT

It will also work when you substitute "M1" with variable containing string (M1 <- "M1").

来源：https://stackoverflow.com/questions/9268154/how-to-use-variable-labels-in-r