Re: [R] How to assign value to a variable dynamically constructed
I'll let Bill respond in detail if he cares to(he is both more knowledgable and fluent at this than I), but as a nearly unbreakable rule, get() and assign() should not be used in R. Basically, they represent a macro (script)-oriented strategy for handling R's objects, whereas R is designed to use an object-oriented (everything is an object) and functional (all procedures are functions) approach. Using get() and assign() leads to messy, confusing, error-prone, non-portable code in R, and that's why they should be avoided. For details, you should consult web tutorials, John Chambers's books, and other books on R programming. Cheers, Bert Bert Gunter Data is not information. Information is not knowledge. And knowledge is certainly not wisdom. -- Clifford Stoll On Fri, Jul 10, 2015 at 9:44 AM, Bastien Tran bastien.t...@gmail.com wrote: Dear all, Provided I understood correctly, shouldn't assign() do the trick? Most similar threads seem to include this approach (among others, indeed). Regards, Bastien On Wednesday, July 8, 2015 at 7:30:04 PM UTC+2, William Dunlap wrote: You can use an environment instead of a list using the same [[ syntax. It is like 'get0(..., inherit=FALSE)' on the left side of the - and like 'assign(...)' on the right side. E.g., myData - new.env() varName - v1 myData[[varName]] - 1:10 myData[[varName]][4] - myData[[varName]][4] * 100 myData[[varName]] # [1] 1 2 3 400 5 6 7 8 9 10 names(myData) # [1] v1 (Before R-3.2.0 or so, you had to use objects(myData,all=TRUE) if myData was an environment and names(myData) if it was a list. Now names() works for environments.) It is better to use a dedicated environment (or list) for each set of related variables so that name collisions do not cause problems. Bill Dunlap TIBCO Software wdunlap tibco.com On Wed, Jul 8, 2015 at 10:06 AM, Greg Snow 538...@gmail.com wrote: This is FAQ 7.21. The most important part of the answer in FAQ 7.21 is the last section where it states that it is often easier to use a list rather than messing around with trying to dynamically name global variables. If you tell us what you are trying to accomplish then we may have better advice. The route you are headed down now usually leads to inefficient code and hard to find bugs. On Tue, Jul 7, 2015 at 2:53 PM, Jun Shen jun.shen...@gmail.com wrote: Dear list, Let's say we have a variable (id), whose name is dynamically constructed. This variable represents a vector or data frame with many elements. Now I want to specifically assign a value to one of the elements. I couldn't get it right. test - 'id' # id is dynamically constructed through paste() id - 1:4 # I can get the element by doing get(test)[2] # Now I want to assign a value to the second element of this dynamical variable. get(test)[2] - 5 # doesn't work. Thanks a lot. Jun Shen [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] How to assign value to a variable dynamically constructed
Dear all, Provided I understood correctly, shouldn't assign() do the trick? Most similar threads seem to include this approach (among others, indeed). Regards, Bastien On Wednesday, July 8, 2015 at 7:30:04 PM UTC+2, William Dunlap wrote: You can use an environment instead of a list using the same [[ syntax. It is like 'get0(..., inherit=FALSE)' on the left side of the - and like 'assign(...)' on the right side. E.g., myData - new.env() varName - v1 myData[[varName]] - 1:10 myData[[varName]][4] - myData[[varName]][4] * 100 myData[[varName]] # [1] 1 2 3 400 5 6 7 8 9 10 names(myData) # [1] v1 (Before R-3.2.0 or so, you had to use objects(myData,all=TRUE) if myData was an environment and names(myData) if it was a list. Now names() works for environments.) It is better to use a dedicated environment (or list) for each set of related variables so that name collisions do not cause problems. Bill Dunlap TIBCO Software wdunlap tibco.com On Wed, Jul 8, 2015 at 10:06 AM, Greg Snow 538...@gmail.com wrote: This is FAQ 7.21. The most important part of the answer in FAQ 7.21 is the last section where it states that it is often easier to use a list rather than messing around with trying to dynamically name global variables. If you tell us what you are trying to accomplish then we may have better advice. The route you are headed down now usually leads to inefficient code and hard to find bugs. On Tue, Jul 7, 2015 at 2:53 PM, Jun Shen jun.shen...@gmail.com wrote: Dear list, Let's say we have a variable (id), whose name is dynamically constructed. This variable represents a vector or data frame with many elements. Now I want to specifically assign a value to one of the elements. I couldn't get it right. test - 'id' # id is dynamically constructed through paste() id - 1:4 # I can get the element by doing get(test)[2] # Now I want to assign a value to the second element of this dynamical variable. get(test)[2] - 5 # doesn't work. Thanks a lot. Jun Shen [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] How to assign value to a variable dynamically constructed
Yes, assign() and get() can do this, but I think the [[]] syntax is simpler and makes it easier to switch between lists and environments for data organization. E.g., the translation of myData[[varName]][4] - myData[[varName]][4] * 100 where myData is an environment to the get/assign style would be something like tmp - get(varName, envir=myData) tmp[4] - tmp[4] * 100 assign(varName, tmp, envir=myData) Bill Dunlap TIBCO Software wdunlap tibco.com On Fri, Jul 10, 2015 at 9:44 AM, Bastien Tran bastien.t...@gmail.com wrote: Dear all, Provided I understood correctly, shouldn't assign() do the trick? Most similar threads seem to include this approach (among others, indeed). Regards, Bastien On Wednesday, July 8, 2015 at 7:30:04 PM UTC+2, William Dunlap wrote: You can use an environment instead of a list using the same [[ syntax. It is like 'get0(..., inherit=FALSE)' on the left side of the - and like 'assign(...)' on the right side. E.g., myData - new.env() varName - v1 myData[[varName]] - 1:10 myData[[varName]][4] - myData[[varName]][4] * 100 myData[[varName]] # [1] 1 2 3 400 5 6 7 8 9 10 names(myData) # [1] v1 (Before R-3.2.0 or so, you had to use objects(myData,all=TRUE) if myData was an environment and names(myData) if it was a list. Now names() works for environments.) It is better to use a dedicated environment (or list) for each set of related variables so that name collisions do not cause problems. Bill Dunlap TIBCO Software wdunlap tibco.com On Wed, Jul 8, 2015 at 10:06 AM, Greg Snow 538...@gmail.com wrote: This is FAQ 7.21. The most important part of the answer in FAQ 7.21 is the last section where it states that it is often easier to use a list rather than messing around with trying to dynamically name global variables. If you tell us what you are trying to accomplish then we may have better advice. The route you are headed down now usually leads to inefficient code and hard to find bugs. On Tue, Jul 7, 2015 at 2:53 PM, Jun Shen jun.shen...@gmail.com wrote: Dear list, Let's say we have a variable (id), whose name is dynamically constructed. This variable represents a vector or data frame with many elements. Now I want to specifically assign a value to one of the elements. I couldn't get it right. test - 'id' # id is dynamically constructed through paste() id - 1:4 # I can get the element by doing get(test)[2] # Now I want to assign a value to the second element of this dynamical variable. get(test)[2] - 5 # doesn't work. Thanks a lot. Jun Shen [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] How to assign value to a variable dynamically constructed
You can use an environment instead of a list using the same [[ syntax. It is like 'get0(..., inherit=FALSE)' on the left side of the - and like 'assign(...)' on the right side. E.g., myData - new.env() varName - v1 myData[[varName]] - 1:10 myData[[varName]][4] - myData[[varName]][4] * 100 myData[[varName]] # [1] 1 2 3 400 5 6 7 8 9 10 names(myData) # [1] v1 (Before R-3.2.0 or so, you had to use objects(myData,all=TRUE) if myData was an environment and names(myData) if it was a list. Now names() works for environments.) It is better to use a dedicated environment (or list) for each set of related variables so that name collisions do not cause problems. Bill Dunlap TIBCO Software wdunlap tibco.com On Wed, Jul 8, 2015 at 10:06 AM, Greg Snow 538...@gmail.com wrote: This is FAQ 7.21. The most important part of the answer in FAQ 7.21 is the last section where it states that it is often easier to use a list rather than messing around with trying to dynamically name global variables. If you tell us what you are trying to accomplish then we may have better advice. The route you are headed down now usually leads to inefficient code and hard to find bugs. On Tue, Jul 7, 2015 at 2:53 PM, Jun Shen jun.shen...@gmail.com wrote: Dear list, Let's say we have a variable (id), whose name is dynamically constructed. This variable represents a vector or data frame with many elements. Now I want to specifically assign a value to one of the elements. I couldn't get it right. test - 'id' # id is dynamically constructed through paste() id - 1:4 # I can get the element by doing get(test)[2] # Now I want to assign a value to the second element of this dynamical variable. get(test)[2] - 5 # doesn't work. Thanks a lot. Jun Shen [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] How to assign value to a variable dynamically constructed
This is FAQ 7.21. The most important part of the answer in FAQ 7.21 is the last section where it states that it is often easier to use a list rather than messing around with trying to dynamically name global variables. If you tell us what you are trying to accomplish then we may have better advice. The route you are headed down now usually leads to inefficient code and hard to find bugs. On Tue, Jul 7, 2015 at 2:53 PM, Jun Shen jun.shen...@gmail.com wrote: Dear list, Let's say we have a variable (id), whose name is dynamically constructed. This variable represents a vector or data frame with many elements. Now I want to specifically assign a value to one of the elements. I couldn't get it right. test - 'id' # id is dynamically constructed through paste() id - 1:4 # I can get the element by doing get(test)[2] # Now I want to assign a value to the second element of this dynamical variable. get(test)[2] - 5 # doesn't work. Thanks a lot. Jun Shen [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
[R] How to assign value to a variable dynamically constructed
Dear list, Let's say we have a variable (id), whose name is dynamically constructed. This variable represents a vector or data frame with many elements. Now I want to specifically assign a value to one of the elements. I couldn't get it right. test - 'id' # id is dynamically constructed through paste() id - 1:4 # I can get the element by doing get(test)[2] # Now I want to assign a value to the second element of this dynamical variable. get(test)[2] - 5 # doesn't work. Thanks a lot. Jun Shen [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] How to assign value to a variable dynamically constructed
Try reading the Help files before posting here. That's what they're for. ?get provides the answer in a note in the Help page. Cheers, Bert Bert Gunter Data is not information. Information is not knowledge. And knowledge is certainly not wisdom. -- Clifford Stoll On Tue, Jul 7, 2015 at 1:53 PM, Jun Shen jun.shen...@gmail.com wrote: Dear list, Let's say we have a variable (id), whose name is dynamically constructed. This variable represents a vector or data frame with many elements. Now I want to specifically assign a value to one of the elements. I couldn't get it right. test - 'id' # id is dynamically constructed through paste() id - 1:4 # I can get the element by doing get(test)[2] # Now I want to assign a value to the second element of this dynamical variable. get(test)[2] - 5 # doesn't work. Thanks a lot. Jun Shen [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
