[R] Repeat elements of matrix based on vector counts

[arun]

Hi,
Try ?merge() or ?join() from library(plyr)
res<-merge(df1,df2,by="plot.id")
 head(res,6)
#  plot.id tree.tag load
#1   plot1      111   17
#2   plot1      112   17
#3   plot1      113   17
#4   plot2      222    6
#5   plot2      223    6
#6   plot3      333   24
A.K>




----- Original Message -----
From: Sarah Haas <haaszoology at gmail.com>
To: r-help at r-project.org
Cc: 
Sent: Thursday, December 13, 2012 9:15 AM
Subject: [R] Repeat elements of matrix based on vector counts

I have two dataframes (df) that share a column header ("plot.id").  In the
1st df, "plot.id" records are repeated a variable number of times based on
the number of trees monitored within each plot. The 2nd df only has a
single record for each "plot.id", and contains a variable named "load" that
is collected at the plot-level and is only listed once per plot record.

*OBJECTIVE:*  I need to repeat the "load" values from the 2nd df based on
how many times "plot.id" is repeated in the 1st df (all plots are repeated
a different number of times). My example dfs are below:

************************************************************************************************
     df1 <- data.frame(plot.id = rep(c("plot1", "plot2", "plot3"),
c(3,2,5)),
                 tree.tag = c(111,112,113,222,223,333,334,335,336,337))

     df2 <- data.frame(plot.id = c("plot1", "plot2", "plot3"), load=c(17,
6, 24))
************************************************************************************************

I have gotten close to solving this, but alas I'm on day 2 of
problem-shooting and can't get it! Thanks for any help you might provide.

--Sarah

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