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I have a data frame that looks something like the one below, which I'll call data frame 1. There is no regular pattern to the number of rows associated with each number in the “tank” column (or the other columns for that matter).

#code for making data frame 1
tank<-c(1,1,2,3,3,3,4,4)
size<-c(2.1,3.5,2.3,4.0,3.3,2.2,1.9,3.0)
mass<-c(6.5,5.5,5.9,7.2,4.9,8.0,9.1,6.3)
df1<-data.frame(cbind(tank,size,mass))

I need to repeat the sequence of values found in the "size" and "mass" columns within each tank. However, the number of repeats for each tank's sequence will differ (again in no particular pattern). I have another data frame (data frame 2) that contains the number of repeats for each tank's sequence, and it looks something like this:

#code for making data frame 2
tank<-c(1,2,3,4)
rpeat<-c(3,1,2,2)
df2<-data.frame(cbind(tank,rpeat))

Ultimately, my goal is to have a data frame like this (see below). Each series of values within a tank is repeated a number of times equal to that specified in data frame 2.

#code for making data frame 3
tank<-c(1,1,1,1,1,1,2,3,3,3,3,3,3,4,4,4,4)
size<-c(2.1,3.5,2.1,3.5,2.1,3.5,2.3,4.0,3.3,2.2,4.0,3.3,2.2,1.9,3.0,1.9,3.0)
mass<-c(6.5,5.5,6.5,5.5,6.5,5.5,5.9,7.2,4.9,8.0,7.2,4.9,8.0,9.1,6.3,9.1,6.3)
df3<-data.frame(cbind(tank,size,mass))

I have figured out a somewhat crude way to do this when each number in the size and mass columns is just repeated a specified number of times (see below) but not how to create the repeating series that I need.

#code to make data frame 4
tank<-c(1,1,1,1,1,1,2,3,3,3,3,3,3,4,4,4,4)
size2<-c(2.1,2.1,2.1,3.5,3.5,3.5,2.3,4.0,4.0,3.3,3.3,2.2,2.2,1.9,1.9,3.0,3.0)
mass2<-c(6.5,6.5,6.5,5.5,5.5,5.5,5.9,7.2,7.2,4.9,4.9,8.0,8.0,9.1,9.1,6.3,6.3)
df4<-data.frame(cbind(tank,size,mass))

To make the above data frame, I took the data frame below, which combines data frames 1 and 2, and applied the code below.

#code to produce data frame 5
tank<-c(1,1,2,3,3,3,4,4)
size<-c(2.1,3.5,2.3,4.0,3.3,2.2,1.9,3.0)
mass<-c(6.5,5.5,5.9,7.2,4.9,8.0,9.1,6.3)
rpeat<-c(3,3,1,2,2,2,2,2)
df5<-data.frame(cbind(tank,size,mass,rpeat))

#code to produce data frame 4 from data frame 5
tank_col <- rep(df5$tank, times = df5$rpeat)
size_col <- rep(df5$size, times = df5$rpeat)
mass_col <- rep(df5$mass, times = df5$rpeat)
goal <-data.frame(cbind(tank_col,size_col,mass_col))

Sorry this is so long, but I have a hard time explaining what I need to do without providing examples. Thanks in advance for any help you can provide.

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1 回答 1

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您可以使用data.table, 和

library(data.table)
# create df1 and df2 as data.tables keyed by tank
DT1 <- data.table(df1, key = 'tank')
DT2 <- data.table(df2, key = 'tank')

# you can now join on tank, and repeat all columns in
# .SD (the subset of the data.table)
DT1[DT2, lapply(.SD, rep, times = rpeat)]


# 1:    1  2.1  6.5
# 2:    1  3.5  5.5
# 3:    1  2.1  6.5
# 4:    1  3.5  5.5
# 5:    1  2.1  6.5
# 6:    1  3.5  5.5
# 7:    2  2.3  5.9
# 8:    3  4.0  7.2
# 9:    3  3.3  4.9
# 10:   3  2.2  8.0
# 11:   3  4.0  7.2
# 12:   3  3.3  4.9
# 13:   3  2.2  8.0
# 14:   4  1.9  9.1
# 15:   4  3.0  6.3
# 16:   4  1.9  9.1
# 17:   4  3.0  6.3

阅读相关的小插曲，data.table以全面了解正在发生的事情。

我们正在做的事情在小插曲中被称为 by-without-by。

于 2013-08-23T02:35:07.407 回答