Convert string to a variable name

Question

I am using R to parse a list of strings in the form   original string  lt -  variable name variable value    First  I extract the variable name and value from the original string and convert the value to numeric class    parameter value  lt - as numeric  variable value   parameter name  lt -  variable name    Then  I would like to assign the value to a variable with the same name as the parameter name string   variable name  lt - parameter value   What is are the function s  for doing this

User · Answer

If you want to convert string to variable inside body of function  but you want to have variable global   test  lt - function     do call   lt  lt -  list  vartest   xxx      test   vartest   1   xxx

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I was working with this a few days ago  and noticed that sometimes you will need to use the get   function to print the results of your variable  ie     varnames   c  jan    feb    march   file names   list files  path to multiple csv files saved on drive   assign varnames 1   read csv file names 1     This will assign the variable   From there  if you try to print the variable varnames 1   it returns  jan    To work around this  you need to do  print get varnames 1

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strsplit to parse your input and  as Greg mentioned  assign to assign the variables   original string  lt - c  x 123    y 456   pairs  lt - strsplit original string       lapply pairs  function x  assign x 1   as numeric x 2    envir   globalenv     ls

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There is another simple solution found there   http   www r-bloggers com converting-a-string-to-a-variable-name-on-the-fly-and-vice-versa-in-r   To convert a string to a variable   x  lt - 42 eval parse text    x     1  42   And the opposite   x  lt - 42 deparse substitute x    1   x

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assign is what you are looking for   assign  x   5   x  1  5   but buyer beware   See R FAQ 7 21 http   cran r-project org doc FAQ R-FAQ html How-can-I-turn-a-string-into-a-variable 003f

User · Answer

Use x as name  quot string quot    You can use then use x to refer to the variable with name string  I don t know  if it answers your question correctly

User · Answer

The function you are looking for is get     assign   abc  5  get  abc     Confirming that the memory address is identical   getabc  lt - get  abc   pryr  address abc     pryr  address getabc     1  TRUE   Reference  R FAQ 7 21 How can I turn a string into a variable

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You can use do call    do call   lt -  list parameter name  parameter value

User · Answer

Maybe I didn t understand your problem right  because of the simplicity of your example  To my understanding  you have a series of instructions stored in character vectors  and those instructions are very close to being properly formatted  except that you d like to cast the right member to numeric   If my understanding is right  I would like to propose a slightly different approach  that does not rely on splitting your original string  but directly evaluates your instruction  with a little improvement    original string  lt -  variable name   10      Your original instruction  but with an actual numeric on the right  stored as character  library magrittr    Or library tidyverse   but it seems a bit overkilled if the point is just to import pipe-stream operator eval parse text paste eval original string      gt   as numeric     print variable name    1  10   Basically  what we are doing is that we  improve  your instruction variable name  10  so that it becomes variable name  10    gt   as numeric  which is an equivalent of variable name as numeric  10   with magrittr pipe-stream syntax  Then we evaluate this expression within current environment   Hope that helps someone who d wander around here 8 years later  -

User · Answer

assign is good  but I have not found a function for referring back to the variable you ve created in an automated script    as name seems to work the opposite way    More experienced coders will doubtless have a better solution  but this solution works and is slightly humorous perhaps  in that it gets R to write code for itself to execute   Say I have just assigned value 5 to x  var name  lt -  x   assign var name  5   and I want to change the value to 6   If I am writing a script and don t know in advance what the variable name  var name  will be  which seems to be the point of the assign function   I can t simply put x  lt - 6 because var name might have been  y    So I do   var name  lt -  x   some other code    assign var name  5   some more code      write a script file  1 line in this case  that works with whatever variable name write paste0 var name     lt - 6     tmp R    source that script file source  tmp R    remove the script file for tidiness file remove  tmp R     x will be changed to 6  and if the variable name was anything other than  x   that variable will similarly have been changed to 6

[string] Convert string to a variable name

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