I am working with the R programming language. I defined the following function and I am trying to perform the "random search" algorithm on this function.

First, I loaded the library:

```
#load library : https://cran.r-project.org/web/packages/randomsearch/index.html
library(randomsearch)
```

Then, I defined the function:

```
# create some data for this example
a1 = rnorm(1000,100,10)
b1 = rnorm(1000,100,10)
c1 = sample.int(1000, 1000, replace = TRUE)
train_data = data.frame(a1,b1,c1)
#define function (4 inputs x[1], x[2], x[3], x[4] and 4 outputs f1, f2, f3, f4)
fn <- function(i) {
x1 <- x[i,1]; x2 <- x[i,2]; x3 <- x[i,3] ; x4 <- x[i,4]
f <- numeric(4)
#bin data according to random criteria
train_data <- train_data %>%
mutate(cat = ifelse(a1 <= x1 & b1 <= x3, "a",
ifelse(a1 <= x2 & b1 <= x4, "b", "c")))
train_data$cat = as.factor(train_data$cat)
#new splits
a_table = train_data %>%
filter(cat == "a") %>%
select(a1, b1, c1, cat)
b_table = train_data %>%
filter(cat == "b") %>%
select(a1, b1, c1, cat)
c_table = train_data %>%
filter(cat == "c") %>%
select(a1, b1, c1, cat)
#calculate quantile ("quant") for each bin
table_a = data.frame(a_table%>% group_by(cat) %>%
mutate(quant = ifelse(c1 > 150,1,0 )))
table_b = data.frame(b_table%>% group_by(cat) %>%
mutate(quant = ifelse(c1 > 300,1,0 )))
table_c = data.frame(c_table%>% group_by(cat) %>%
mutate(quant = ifelse(c1 > 400,1,0 )))
f1 = mean(table_a$quant)
f2 = mean(table_b$quant)
f3 = mean(table_c$quant)
#group all tables
final_table = rbind(table_a, table_b, table_c)
# calculate the total mean : this is what needs to be optimized
f4 = mean(final_table$quant)
#add some constraints
if((x3 - x1) < 0. | (x4 - x2) < 0.) {
f[1] <- NaN
f[2] <- NaN
f[3] <- NaN
f[4] <- NaN
}
return (f)
}
```

Finally, I tried to run the "random search" algorithm on this function:

```
#run algorithm
res = randomsearch(fn, lower = c(80, 80, 80, 80), upper = c(100,120,100,120), minimize = c(TRUE, TRUE, TRUE, TRUE), max.evals = 30)
rs = summary(res)
```

But this resulted in the following error:

```
Error in fun(x, ...) : unused argument (x)
```

Does anyone know why this error is being produced? Is it related to the way I have defined the function "fn"?

Thanks