variable name question
On Oct 9, 2011, at 2:24 PM, Carlos Ortega wrote:
Hello, In R you just need to take the log of the whole whole data.frame where you have your pci* and store in a new variable. You do not need to use a "for" loop: log.df <- log(your_data_frame)
Possibly with a selection for the column names in question:
log.pci.df <- log( your_data_frame[ , grep("^pci",
names(your_data_frame) ) ]
You can also cbind() your identifiers and covariates columns to the
result.
David.
>
> Regards,
> Carlos Ortega
> www.qualityexcellence.es
>
>
> On Sun, Oct 9, 2011 at 5:34 PM, deepankar <dbasu at econs.umass.edu>
> wrote:
>
>> Hi All,
>>
>> This is surely an easy question but somehow I am not being able to
>> get it.
>>
>> I am using R 2.13.2 and have a data set where variable names like
>> this
>> appear:
>>
>> pci1990, pci1991, ... , pci2009.
>>
>> "pci1990" has data on per capita income for 1990, "pci1991" has
>> data on per
>> capita income for 1991, and so on.
>>
>> I would like to create the logarithm of per capita for each of the
>> year and
>> could do so in STATA with the following commands:
>>
>> forvalues number = 1990/2009 {
>> gen lpci`number' = log(pci`number')
>> }
>>
>> What would be the corresponding set of commands in R?
>>
>> Thanks a lot in advance.
>>
>> Deepankar
>>
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>
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David Winsemius, MD
West Hartford, CT