This function generates sequences along the spectra (rows) or wavelengths of
`hyperSpec`

objects.

```
# S3 method for hyperSpec
seq(x, from = 1, to = nrow(x), ..., index = FALSE)
```

- x
the

`hyperSpec`

object- from, to
arguments handed to

`base::seq.int()`

- ...
arguments for

`base::seq()`

, namely`by`

,`length.out`

- index
should a vector with indices be returned rather than a

`hyperSpec`

object?

a numeric or `hyperSpec`

object, depending on `index`

.

Note that `wl2i()`

generates sequences of indices along the wavelength axis.

`seq()`

had to be implemented as S3 method as the generic has only ...
arguments (on which no dispatch with differing types is possible).

`base::seq_along()`

is not generic, but returns a sequence of the `length`

of the object. As `hyperSpec`

provides a Method `length()`

, it can be used.
The result is a sequence of indices for the spectra.

`wl2i()`

to construct sequences of wavelength indices.

```
seq(flu, index = TRUE)
#> [1] 1 2 3 4 5 6
seq_along(flu)
#> [1] 1 2 3 4 5 6
seq(flu, length.out = 3, index = TRUE) # return value is numeric, not integer!
#> [1] 1.0 3.5 6.0
seq(flu, by = 2, index = TRUE) # return value is numeric, not integer!
#> [1] 1 3 5
plot(flu, col = "darkgray")
plot(seq(flu, by = 2), add = TRUE, col = "red")
plot(seq(flu, length.out = 2), add = TRUE, col = "blue")
### needs to be an S3 function as S4 ... dispatch has to have the same
### signature for all parameters
```