[R] R - Populate Another Variable Based on Multiple Conditions | For a Large Dataset

[Jeff Newmiller]

You are making this hard on yourself by not paying attention the Posting Guide listed in the footer of every email on this list. You would probably also find [1] helpful also. 

[1] http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example
-- 
Sent from my phone. Please excuse my brevity.

On July 2, 2016 3:41:07 PM PDT, Kevin Wamae <KWamae at kemri-wellcome.org> wrote:
>Hi Jeff, sorry for referring to you as Jennifer earlier, accept my
>apologies.
>
>I attached a sample dataset in the question, am afraid it must have
>failed to attach.
>
>I have attached it again..
>
>
>Regards
>-------------------------------------------------------------------------------
>Kevin Kariuki
> 
>
>On 7/2/16, 7:37 PM, "Jeff Newmiller" <jdnewmil at dcn.davis.ca.us> wrote:
>
>I can understand you not wanting to supply your actual data online, but
>only you know what your data looks like so only you can create a
>simulated data set that we could show you how to work with. 
>-- 
>Sent from my phone. Please excuse my brevity.
>
>On July 2, 2016 2:57:39 AM PDT, Kevin Wamae <KWamae at kemri-wellcome.org>
>wrote:
>>I have a drug-trial study dataset (attached image).
>>
>>Since its a large and complex dataset (at least to me) and I hope to
>be
>>as clear as possible with my question.
>>The dataset is from a study where individuals are given drugs and
>>followed up over a period spanning two consecutive years. Individuals
>>do not start treatment on the same day and once they start, the
>>variable "drug-admin" is marked "x" as well as the time they stop
>>treatment in the following year.
>>There exists another variable, "study_id", that I hope to populate as
>>can be seen in the dataset, with the following conditions:
>>
>>For every individual
>>•    if the individual has entries that show they received drugs both
>>on the start and end date (marked with the "x")
>>•    if the start of drug administration falls in month == 2 | 3 and
>>end of administration falls in month == 2 | 4
>>•    then, using the date that marks the start of drug administration,
>>populate the variable _"study_id"_ in all the rows that fall within
>the
>>timeframe that the individual was given drugs but excluding the end of
>>drug administration.
>>I have tried my level best and while I have explored several examples
>>online, I haven't managed to solve this. The dataset contains close to
>>6000 individuals spanning 10 years and my best bet was to use a loop
>>which keeps crushing R after running for close to 30min. I have also
>>read that dplyr may do the job but my attempts have been in vain.
>>
>>sample code
>>-------------------------------------------------------------------------------------------------------------------------------------------------------------------
>>individual <- unique (df$ID)  #vector of individuals
>>datalength <- dim(df)[1]      #number of rows in dataframe
>>
>>for (i in 1:length(individual)) {
>>  for (j in 1:datalength) {
>>start_admin <- df[(df$year == 2007] & df$drug_admin == "x" &
>c(df$month
>>== 2 | df$month == 3),1]  #capture date of start
>>end_admin <- df[(df$year == 2008] & df$drug_admin == "x" & c(df$month
>>== 2 | df$month == 4),1]    #capture date of end
>>
>>if(df[datalength,1] == individual(i) & df[datalength,2] >= start_admin
>>& df[datalength,2] < end_admin) {
>>df[datalength,6] <- start_admin #populate respective row if condition
>>is met
>>      }
>>    }
>>  }
>>
>>-------------------------------------------------------------------------------------------------------------------------------------------------------------------
>>
>>Above is the code that keeps failing..
>>
>>Any help is highly appreciated....
>>
>>
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