[R] how to get a value from a list (using paste function)?

[Uwe Ligges]

On 27.12.2012 13:04, Heramb Gadgil wrote:
> Agreed.
>
> But the initial question was to get the output with paste function. That is
> the reason why I went for eval.
>
> Please let me know in case I am going the wrong way

You solution is valid to answer the question. But the original poster 
probably does not know there is a better way than pasting strings 
together. And we should point him to the best solution for handling his 
problem, not the suboptimal one he was looking for initially.

Best,
Uwe Ligges



>
> On Thu, Dec 27, 2012 at 4:34 PM, Jessica Streicher <j.streicher at micromata.de
>> wrote:
>
>> Well for one, if ever someone looks at your code, cvtest[[lambda.rule]] is
>> much easier to read and understand than
>> eval(parse(text=paste0("cvtest$",lambda.rule)))
>>
>>
>> On 27.12.2012, at 11:44, Heramb Gadgil wrote:
>>
>>> I am not sure why "Never ever!"
>>>
>>> Can you please elaborate. What are the negatives about the method
>>>
>>> Warm Regards,
>>> Heramb M. Gadgil
>>>
>>>
>>> On Thu, Dec 27, 2012 at 3:50 PM, Uwe Ligges <
>> ligges at statistik.tu-dortmund.de
>>>> wrote:
>>>
>>>>
>>>>
>>>> On 27.12.2012 08:09, Heramb Gadgil wrote:
>>>>
>>>>> eval(parse(text=paste0("**cvtest$",lambda.rule)))
>>>>>
>>>>
>>>> No, never ever!
>>>>
>>>> There is an R idiom made for it:
>>>>
>>>> cvtest[[lambda.rule]]
>>>>
>>>> Uwe Ligges
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> I hope this works.
>>>>>
>>>>> On Wed, Dec 19, 2012 at 12:57 AM, Thomas Stewart
>>>>> <tgs.public.mail at gmail.com>**wrote:
>>>>>
>>>>> Soyeon-
>>>>>>
>>>>>> A possible solution:
>>>>>>
>>>>>> get(lambda.rule,envir=**list2env(cvtest))
>>>>>>
>>>>>>
>>>>>> On Tue, Dec 18, 2012 at 12:34 PM, Soyeon Kim <yunni0731 at gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>> Dear my R friends,
>>>>>>>
>>>>>>> I want to get a number from a list using paste function.
>>>>>>> In my example,
>>>>>>> lambda.rule <- "lambda.1se"
>>>>>>> cvtest is a list (result from cv.glmnet)
>>>>>>> and
>>>>>>> cvtest$lambda.1se
>>>>>>> [1] 1.308973
>>>>>>>
>>>>>>> I want to call the value using paste function.
>>>>>>> I used get function but there was an error.
>>>>>>> test <-  get(paste("cvtest$",lambda.**rule, sep=""))
>>>>>>> Error in get(paste("cvtest$", lambda.rule, sep = "")) :
>>>>>>>    object 'cvtest$lambda.1se' not found
>>>>>>>
>>>>>>> Do you guys know how to solve this issue?
>>>>>>>
>>>>>>> Thank you so much in advance and merry Christmas!
>>>>>>>
>>>>>>> Soyeon
>>>>>>>
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>>>>>>>
>>>>>>>
>>>>>>>
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>>
>