Hello, I want to train a `Neural Network`

and pass it a custom error measure function.

For example, I tried the following:

```
rmse = function(error) sqrt(mean(error ^ 2))
nn <- neuralnet(score ~ ., data = ds_trn_noc, hidden = 2, err.fct = rmse)
```

but got the following error:

```
Error in eval(expr) : generic 'function' is not a function
```

My goal is that when I run the command:

```
> nn$result.matrix
```

I get the following output:

```
## [,1]
## error 1.988157e+02
## reached.threshold 9.903357e-03
## steps 4.576900e+04
...
...
...
```

where the error is calculated by my custom function: `rmse`

.

Any idea about what's wrong on my code above?

Thanks!