Insert values to a vector at certain positions

Insert values to a vector at certain positions.

# S3 method for default
insert(x, ats, values=NA, useNames=TRUE, ...)

Arguments

x

The vector of data values.

ats

The indices of x where the values should be inserted.

values

A list or a vector of the values to be inserted. Should be of same length as ats, unless if a single value when it is automatically extended without a warning.

useNames

If FALSE, the names attribute is dropped/ignored, otherwise not. Only applied if argument x is named.

...

Not used.

See also

append() takes argument after (a scalar). For example, append(x, y, after=after) == insert(x, values=y, ats=after+1). Contrary to append(), insert() accepts a vector of insert indices.

Author

Henrik Bengtsson

Examples

# Insert NAs (default) between all values
y <- c(a=1, b=2, c=3)
print(y)
#> a b c 
#> 1 2 3 
x <- insert(y, ats=2:length(y))
Ex <- c(y[1], NA_real_, y[2], NA_real_, y[3])
print(x)
#>  a     b     c 
#>  1 NA  2 NA  3 
stopifnot(identical(x,Ex))

# Insert at first position
y <- c(a=1, b=2, c=3)
print(y)
#> a b c 
#> 1 2 3 
x <- insert(y, ats=1, values=rep(NA_real_,2))
Ex <- c(NA_real_,NA_real_,y)
print(x)
#>        a  b  c 
#> NA NA  1  2  3 
stopifnot(identical(x,Ex))

x <- insert(y, ats=1, values=rep(NA_real_,2), useNames=FALSE)
print(x)
#> [1] NA NA  1  2  3

# Insert at last position (names of 'values' are ignored
# because input vector has no names)
x <- insert(1:3, ats=4, values=c(d=2, e=1))
Ex <- c(1:3,2,1)
print(x)
#> [1] 1 2 3 2 1
stopifnot(identical(x,Ex))


# Insert in the middle of a vector
x <- insert(c(1,3,2,1), ats=2, values=2)
print(x)
#> [1] 1 2 3 2 1
stopifnot(identical(as.double(x),as.double(Ex)))


# Insert multiple vectors at multiple indices at once
x0 <- c(1:4, 8:11, 13:15)

x <- insert(x0, ats=c(5,9), values=list(5:7,12))
print(x)
#>  [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
Ex <- 1:max(x)
stopifnot(identical(as.double(x),as.double(Ex)))

x <- insert(x0, ats=c(5,9,12), values=list(5:7,12,16:18))
print(x)
#>  [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18
Ex <- 1:max(x)
stopifnot(identical(as.double(x),as.double(Ex)))


# Insert missing indices
Ex <- 1:20
missing <- setdiff(Ex, x0)
x <- x0
for (m in missing)
  x <- insert(x, ats=m, values=m)
print(x)
#>  [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20
stopifnot(identical(as.double(x),as.double(Ex)))