`tfb` edge cases

[m-muecke]

• the printer with length one seems wrong (nothing comes after using)
• length one tfb can't be created
• length two tfb gives an error from another package

tf::tfb()
#> tfb[0] on (0,0) in basis representation:
#>  using
tf::tfb(1)
#> Error in new_tfb_spline(data, domain = domain, penalized = penalized, : Assertion on 'domain' failed: Contains duplicated values, position 2.
tf::tfb(1:2)
#> Warning in smooth.construct.cr.smooth.spec(s_spec, data = data_frame(arg = arg_u$x, : basis dimension, k, increased to minimum possible
#> Error in smooth.construct.cr.smooth.spec(s_spec, data = data_frame(arg = arg_u$x, : arg has insufficient unique values to support 3 knots: reduce k.
tf::tfb(1:3)
#> Percentage of input data variability preserved in basis representation
#> (per functional observation, approximate):
#> Min. 1st Qu.  Median Mean 3rd Qu.  Max.
#> 100 100 100 100 100 100
#> tfb[1] on (1,3) in basis representation:
#>  using  s(arg, bs = "cr", k = 3, sp = -1)  
#> 1: (1,1);(2,2);(3,3)

^{Created on 2024-11-10 with reprex v2.1.1}

[fabian-s]

:see_no_evil: thanks!

• re print statement for empty tfb: I can live with that.

• re tfb of length 1 with just 1 or 2 args: a basis rep just can't make sense for these/can't be computed sensibly. inclined towards returning an error here, even if this looks superficially inconsistent with allowing empty tfbs. I'll take a closer look at this myself.