R: Error in fn(unlist(x), ...) : unused argument (unlist(x))

Question

I am using the "mlrMBO" library in R (https://cran.r-project.org/web/packages/mlrMBO/index.html). I am trying to learn how to run an optimization algorithm on some arbitrary function that I defined:

#Load library
library(mlrMBO)

#define objective function
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 = makeParamSet(
     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 | x3 > x4)
),

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)

This code returns the following error:

Error in fn(unlist(x), ...) : unused argument (unlist(x))

Does anyone know why this error is being produced? I have tried to look at various reference material (e.g. https://cran.r-project.org/web/packages/mlrMBO/mlrMBO.pdf and https://cran.r-project.org/web/packages/mlrMBO/vignettes/mlrMBO.html), but so far I am unable to understand why this error is being produced.

Can someone please show me what am I doing wrong?

Thanks

Answer 1

You need to add one setting and adjust another one:

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 = makeParamSet(
    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 | x3 > x4)
  ),
  
  minimize=rep(TRUE, 3), #corrected
  has.simple.signature = FALSE #added
)