I am working with the R programming language. I am learning how to use the "mlrMBO" library for the purpose of optimizing multi-objective functions (using Bayesian Methods).

In my example, for the following constraints:

```
x2 >x1 AND x4 >x3
```

I want to optimize the following (multi-objective) function I defined:

```
bayesian_function <- function(x1, x2, x3, x4) {
var_1 <- sin(x1 + x2)
var_2 <- cos(x1 - x2)
var_3 <- x1 + x4
var_4 <- x3 + x4 -7
goal_1 = sum(var_1 + var_2 + var_3 + var_4)
goal_2 = var_1 + var_2 - var_3 + var_4
goal_3 = var_1 + var_2 - var_3 + 2*var_4
return(c(goal_1, goal_2, goal_3))
}
```

To do this, I tried the follow the necessary "mlrMBO" syntax to optimize this function for the given constraints and allowed ranges for "x1, x2, x3, x4" :

```
#load libraries
library(mlrMBO)
library(ParamHelpers)
library(smoof)
obj.fn = makeMultiObjectiveFunction(
name = "My test function",
fn = function(x1, x2, x3, x4) {
var_1 <- sin(x1 + x2)
var_2 <- cos(x1 - x2)
var_3 <- x1 + x4
var_4 <- x3 + x4 -7
goal_1 = sum(var_1 + var_2 + var_3 + var_4)
goal_2 = var_1 + var_2 - var_3 + var_4
goal_3 = var_1 + var_2 - var_3 + 2*var_4
return(c(goal_1, goal_2, goal_3))
},
#define acceptable ranges
par.set = makeNumericParamSet(
makeNumericParam("x1", lower = 20, upper = 40),
makeNumericParam("x2", lower = 30, upper = 45),
makeNumericParam("x3", lower = 10, upper = 20),
makeNumericParam("x4", lower = 10, upper = 50),
#define constraints
forbidden = expression(x2 >x1),
forbidden = expression(x4 >x3)
),
minimize=TRUE
)
#create control gird
control=makeMBOControl(propose.points=1, final.method="best.predicted", final.evals=10)
control=setMBOControlTermination(control, iters=10)
control=setMBOControlInfill(control, crit=makeMBOInfillCritEI())
#perform optimization
lrn=makeMBOLearner(control, obj.fun)
```

The first part of this code returns the following error and preventing me from running the rest of the code:

```
Error in makeNumericParamSet(makeNumericParam("x1", lower = 20, upper = 40), :
unused arguments (forbidden = expression(x2 > x1), forbidden = expression(x4 > x3))
```

It seems that there is a problem while defining the constraints (i.e. "forbidden" statement). I tried reading more about this function makeParamSet function - RDocumentation , but I can't seem to figure out what I am doing wrong.

Can someone please show me why this error is being produced?

Thanks