I wonder if `partkykit::ctree`

function ignores variables with non syntactic names or am I missing something?

Toy example:

```
myData<-data.frame(
Y = factor(rep(LETTERS[1:3], each=10)),
x1 = 1:30,
x2 = c(1:10,2:11,3:12)
)
```

Clearly `x1`

is the best "predictor" of `Y`

:

```
ctree(Y~., data=myData)
Model formula:
Y ~ x1 + x2
Fitted party:
[1] root
| [2] x1 <= 10: A (n = 10, err = 0,0%)
| [3] x1 > 10
| | [4] x1 <= 20: B (n = 10, err = 0,0%)
| | [5] x1 > 20: C (n = 10, err = 0,0%)
Number of inner nodes: 2
Number of terminal nodes: 3
```

But when I change it's name to non syntactic one, it seems to be ignored in tree construction process:

```
myData<-data.frame(
Y = factor(rep(LETTERS[1:3], each=10)),
`x 1` = 1:30,
x2 = c(1:10,2:11,3:12),
check.names = F
)
ctree(Y~., data=myData)
Model formula:
Y ~ `x 1` + x2
Fitted party:
[1] root: A (n = 30, err = 66,7%)
Number of inner nodes: 0
Number of terminal nodes: 1
```

Can you suggest any way to overcome this behaviour ('cos I really-really-really wish to use `x 1`

as a name, don't ask why)?

`party::ctree`

but not for`partykit::ctree`