[R] How to automatically create data frames from an existing one?

[MacQueen, Don]

I don't know what the matlab eval() function does, but this example might help you get started with the way R does things:

lapply( rwrdatafile, summary)

This will apply the summary() function to every column of the data frame.

As others have mentioned, it is bad R to create separate variables for each column of the data frame. Anything you want to do with your variable named wage you can do with rwdatafile$wage. Regression analysis even more you should NOT take the variables out of the data frame. Instead using things like
  lm( wage ~ year, data=rwdatafile)

But if you insist on it, then try this:

for (nm in names(rwrdatafile)) assign(nm, rwrdatafile[[nm]], '.GlobalEnv')

(assuming I got the parentheses matched correctly)

-- 
Don MacQueen

Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062


On 1/11/17, 3:53 AM, "R-help on behalf of Tunga Kantarcı" <r-help-bounces at r-project.org on behalf of tungakantarci at gmail.com> wrote:

    I have a data frame that includes several columns representing
    variables and variables names are indicated at the top row of the data
    frame. That is, I had a csv file where variable names were stored in
    the top row, and when I imported the csv file to R, R created a data
    frame that appears with the name rwrdatafile (custom name I gave)
    where I can see all the variables with their names on the top row in
    RStudio. For example, one of the columns stores wage data and I can
    create a stand alone data frame (shall I call it a vector data frame?)
    for wage, but do this for all variables.
    
    That is, I can execute the command
    
    wage = rwrdatafile[,1,drop=FALSE]
    
    which nicely creates wage and RStudio shows it as data in its
    environment window and if I click on it, I can inspect it in a spread
    sheet like view and work with that data say in regression analysis.
    
    The problem is that there are many variables stored in the data frame
    rwrdatafile, and it is very tedious to repeat the above mentioned
    routine for each variable. Hence I attempted to write a for loop for
    this but it helped to no avail.
    
    In particular, I tried
    
    for (i in 1:k){
      assign(names(rwrdatafile)[i],rwrdatafile[,i])
    }
    
    and in fact this nicely assigns each column in the data frame to a
    name, but I do not see the variables as data in the environment
    section. But what I need are variables that I can work with in matrix
    operations.
    
    I also tried
    
    for(i in 1:k){
      names(rwrdatafile)[i] = rwrdatafile[,i,drop=FALSE]
    }
    
    thinking that this for loop would just repeat what I do for
    
    wage = rwrdatafile[,1,drop=FALSE]
    
    for all the variables in rwrdatafile.
    
    Please note that I do need to use a for loop and in fact I need to
    translate and imitate the MATLAB code below, which does the job in
    MATLAB, as close as possible in R.
    
    # MATLAB code generating variables from structure array rwrdatafile
    [N,k] = size(rwrdatafile.data);
    for i = 1:k
        eval([cell2mat(rwrdatafile.textdata(i)) '= rwrdatafile.data(:,i);'])
    end
    
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