How to use `assign ()` or `get ()` in a specific named column for dataframe?

Question

Is there a way to assign a value to a specific column in a data frame? eg.

dat2 = data.frame(c1 = 101:149, VAR1 = 151:200) j = "dat2[,"VAR1"]" ## or, j = "dat2[,2]" assign(j,1:50) 

The above approach does not work. It also does not:

 j = "dat2" assign(get(j)[,"VAR1"],1:50) 

Answer 1

suggests that we have a valid data.frame with 50 rows in each

 dat2 <- data.frame(c1 = 1:50, VAR1 = 51:100) 

1. Do not use assign and get if you can avoid this.

"dat2[,"VAR1"]" not valid in R

You can also mark this from the help page for assign

assign does not send assignment methods, so it cannot be used to set vector elements, names, attributes, etc.

Note that assigning a linked list or data frame changes the attached copy, not the original object: see attachment and p.

The data.frame column is a list item.

What you are looking for is [[<-

 # assign the values from column (named element of the list) `VAR1` j <- dat2[['VAR1']] 

If you want to assign new values ​​to VAR1 inside dat2 ,

 dat2[['VAR1']] <- 1:50 

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The answer to your question....

To fully manipulate character strings with get and assign

 assign('dat2', `[[<-`(get('dat2'), 'VAR1', value = 2:51)) 

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Other approaches

data.table :: set

if you want to assign by reference in data.frame or data.table (instead of the existing column only), then set from the data.table package works (even with data.frames )

 library(data.table) set(dat2, j = 'VAR1', value = 5:54) 

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eval and bquote

 dat1 <- data.frame(x=1:5) dat2 <- data.frame(x=2:6) for(x in sapply(c('dat1','dat2'),as.name)) { eval(bquote(.(x)[['VAR1']] <- 2:6)) } 

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eapply

Or if you are using a separate environment

 ee <- new.env() ee$dat1 <- dat1 ee$dat2 <- dat2 # eapply returns a list, so use list2env to assign back to ee list2env(eapply(ee, `[[<-`, 'y', value =1:5), envir = ee) 

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Answer 2

 set2 <- function(x, val) { eval.parent(substitute(x <- val)) } > dat2 = data.frame(c1 = 101:150, VAR1 = 151:200) > set2(dat2[["VAR1"]], 1:50) > str(dat2) 'data.frame': 50 obs. of 2 variables: $ c1 : int 101 102 103 104 105 106 107 108 109 110 ... $ VAR1: int 1 2 3 4 5 6 7 8 9 10 ...