The data frame I have contains two colum: ID and type (character). See below:
set.seed(123)
ID <- seq(1,25)
type <- sample(letters[1:26], 25, replace=TRUE)
df <- data.frame(ID, type)
I need to create a new data frame that contain only one column. The first observation will be the first three letters in column type, the second observation is the second three letters, and soon on.
The new data looks like
ndf <- data.frame(ntype=c("huk", "wyb", "nxo", "lyl", "roc", "xgb", "iyx", "sqz", "r"))
1) rollapply along the input vector:
library(zoo)
rollapply(df$type, 3, by = 3, paste, collapse = "", partial = TRUE, align = "left")
giving:
[1] "huk" "wyb" "nxo" "lyl" "roc" "xgb" "iyx" "sqz" "r"
2) This alternative uses aggregate and no packages.
n <- nrow(df)
aggregate(type ~ gl(n, 3, n), df, paste, collapse = "")[2]
giving:
type
1 huk
2 wyb
3 nxo
4 lyl
5 roc
6 xgb
7 iyx
8 sqz
9 r
We create a grouping variable with gl and then with tapply, paste the elements together
n <- 3
ndf <- data.frame(ntype = with(df, unname(tapply(type, as.integer(gl(nrow(df), n,
nrow(df))), FUN =paste, collapse=""))), stringsAsFactors= FALSE)
ndf$ntype
#[1] "huk" "wyb" "nxo" "lyl" "roc" "xgb" "iyx" "sqz" "r"
Or another option is to paste the whole column together and then split
strsplit(paste(df$type, collapse=""), "(?<=.{3})", perl = TRUE)[[1]]
#[1] "huk" "wyb" "nxo" "lyl" "roc" "xgb" "iyx" "sqz" "r"
Or another option is substring with paste
substring(paste(df$type, collapse=""), seq(1, nrow(df), by = 3),
c(seq(3, nrow(df), by = 3), nrow(df)))
#[1] "huk" "wyb" "nxo" "lyl" "roc" "xgb" "iyx" "sqz" "r"
Note: All the above are base R solutions
By using dplyr
df$group=(df$ID-1)%/%3
df%>%group_by(group)%>%dplyr::summarise(ntype=paste0(type,collapse = ''))
# A tibble: 9 x 2
group ntype
<dbl> <chr>
1 0 huk
2 1 wyb
3 2 nxo
4 3 lyl
5 4 roc
6 5 xgb
7 6 iyx
8 7 sqz
9 8 r