dataframe - R: Insert multiple rows (variable number) in data frame -

i have data frame with, say, 5 rows, 2 observables. need insert "dummy" or "zero" rows in data frame number of rows per observable same (and can bigger n rows longer one). e.g.:

#   have: x = c("a","a","b","b","b") y = c(2,4,5,2,6) dft = data.frame(x,y) print(dft)    x y 1 2 2 4 3 b 5 4 b 2 5 b 6 

here's i'd get, i.e. add n rows per observable 4. mock df

x1 = c("a","a","a","a","b","b","b","b") y1 = c(2,4,0,0,5,2,6,0) dft1 = data.frame(x1,y1) print(dft1)    x1 y1 1   2 2   4 3   0 4   0 5  b  5 6  b  2 7  b  6 8  b  0 

i started getting n rows in original data frame per observable ddply, know how many rows need add each observable.

library(plyr) nr = ddply(dft,.(x),summarise,val=length(x)) print(nr)    x val 1   2 2 b   3   # n extras 2 , 1 reach 4 per obs.   repl      = 4 - nr$val repl_name = nr$x repl_x    = rep(repl_name,repl)  print(repl_x)  [1] a b levels: b  dfa = matrix("-",nrow=sum(repl),ncol=1) dff = data.frame(repl_x,as.data.frame(dfa))  names(dff) <- names(dft) dft = rbind(dft,dff) dft = dft[order(as.character(dft$x)),]  print(dft)    x y 1 2 2 4 6 - 7 - 3 b 5 4 b 2 5 b 6 8 b - 

i did achieve goal, in quite few operations , transformations.

so, question - there simpler , faster way insert arbitrary number of empty/dummy rows in several places in data frame. number of columns , rows can any.

note: code above works, believe question not "review code" type, genuine - "how better" question. thank you!

you can try using "data.table" package let use "length<-" expand out rows.

demo:

library(data.table) as.data.table(dft)[, lapply(.sd, `length<-`, 4), = x] ##    x  y  z ## 1:  2  2 ## 2:  4  3 ## 3: na na ## 4: na na ## 5: b  5  4 ## 6: b  2  5 ## 7: b  6  6 ## 8: b na na 

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update

upon provocation thela-the-taunter™, if want stick base r, perhaps can create function following:

narowsbygroup <- function(indf, group, rowsneeded) {   do.call(rbind, lapply(split(indf, indf[[group]]), function(x) {     x <- data.frame(lapply(x, `length<-`, rowsneeded))     x[group] <- x[[group]][1]     x   })) } 

usage be:

narowsbygroup(dft, 1, 4) #   x  y  z # 1  2  2 # 2  4  3 # 3 na na # 4 na na # 5 b  5  4 # 6 b  2  5 # 7 b  6  6 # 8 b na na 

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sample data:

x = c("a","a","b","b","b") y = c(2,4,5,2,6) z = c(2,3,4,5,6) dft = data.frame(x,y,z)