[R] Faster way to combine data sets with different date ranges
ggrothendieck at gmail.com
Sat Nov 8 00:38:15 CET 2008
See ?merge. Also ?merge.zoo in the zoo package and sqldf
in the sqldf package (http://sqldf.googlecode.com).
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On Fri, Nov 7, 2008 at 6:19 PM, t c <mudiver1200 at yahoo.com> wrote:
> I am trying to combine two data sets, one with daily values and one with weekly values. SurveyData conatins environmental data collected on a daily basis. sat.data contains satellite sea surface temperature that is an average of satellite measurements over a six day period. I would like to combine the two files so that my output file has the daily dates from SurveyData and the weekly average from sat.data that corresponds to that day. I have written a loop that does exactly what I want, but it takes a very long time. Is there a faster way to do this? What I have so far is below.
> #Compare dates
> for(i in 1:length(SurveyData$Date))
> for(j in 1:length(sat.data$Date.Start))
> sat.data$Date.Start[j]<=SurveyData$Date[i] &
> survey.data[i]<- sat.data$data[j]
> #Create data frame with final data
> #Write data to file
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