How to name variables on the fly

Question

Is it possible to create new variable names on the fly   I d like to read data frames from a list into new variables with numbers at the end  Something like orca1  orca2  orca3     If I try something like  paste  orca  i sep     list name  i     I get this error  target of assignment expands to non-language object   Is there another way around this

User · Accepted Answer

Use assign   assign paste  orca   i  sep        list name  i

User · Answer

Another tricky solution is to name elements of list and attach it   list name   list      head iris       head swiss       head airquality         names list name   lt - paste  orca   seq along list name   sep     attach list name   orca1     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

User · Answer

Don t make data frames  Keep the list  name its elements but do not attach it   The biggest reason for this is that if you make variables on the go  almost always you will later on have to iterate through each one of them to perform something useful  There you will again be forced to iterate through each one of the names that you have created on the fly   It is far easier to name the elements of the list and iterate through the names    As far as attach is concerned  its really bad programming practice in R and can lead to a lot of trouble if you are not careful

User · Answer

And this option   list name lt -list   for i in 1 100       paste  orca  i sep    - gt list name  i       It works perfectly  In the example you put   first line is missing  and then gives you the error message

User · Answer

It seems to me that you might be better off with a list rather than using orca1  orca2  etc      then it would be orca 1   orca 2        Usually you re making a list of variables differentiated by nothing but a number because that number would be a convenient way to access them later   orca  lt - list   orca 1   lt -  Hi  orca 2   lt - 59   Otherwise  assign is just what you want

User · Answer

FAQ says   If you have  varname  lt - c  a    b    d     you can do  get varname 1     2   for  a   2   or  assign varname 1   2   2    for  a  lt - 2   2   So it looks like you use GET when you want to evaluate a formula that uses a variable  such as a concatenate   and ASSIGN when you want to assign a value to a pre-declared variable    Syntax for assign   assign x  value   x  a variable name  given as a character string  No coercion is done  and the first element of a character vector of length greater than one will be used  with a warning   value  value to be assigned to x

[r] How to name variables on the fly?

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