Set control parameters for `loess`

fits.

```
loess.control(surface = c("interpolate", "direct"),
statistics = c("approximate", "exact", "none"),
trace.hat = c("exact", "approximate"),
cell = 0.2, iterations = 4, iterTrace = FALSE, …)
```

surface

should the fitted surface be computed exactly
(`"direct"`

) or via interpolation from a kd tree? Can be abbreviated.

statistics

should the statistics be computed exactly, approximately or not at all? Exact computation can be very slow. Can be abbreviated.

trace.hat

Only for the (default) case ```
(surface =
"interpolate", statistics = "approximate")
```

: should the trace of
the smoother matrix be computed exactly or approximately? It is recommended to use the approximation
for more than about 1000 data points. Can be abbreviated.

cell

if interpolation is used this controls the accuracy of the
approximation via the maximum number of points in a cell in the kd
tree. Cells with more than `floor(n*span*cell)`

points are subdivided.

iterations

the number of iterations used in robust fitting,
i.e. only if `family`

is `"symmetric"`

.

iterTrace

logical (or integer) determining if tracing
information during the robust iterations (`iterations`

\(\ge
2\)) is produced.

…

further arguments which are ignored.

A list with components