Running examples in 'gripp-Ex.R' failed
The error most likely occurred in:

> base::assign(".ptime", proc.time(), pos = "CheckExEnv")
> ### Name: cost
> ### Title: Cost function
> ### Aliases: cost
> 
> ### ** Examples
> 
> # number of parameters.
> n <- 2
> #
> # Configure the name of the folder where each file with the parameter to be changed.
> # If the folder is 'wd' then it will not be changed.
> # You can change it to another location where your parameter files are.
> auxi <- system.file(package = "gripp")
> folder_name <- c(auxi,auxi)
> #
> # Configure the name of each file to be changed in the Direct Problem Solver.
> file_name <- c('f1.R','f1.R')
> #
> # Configure the name of each parameter to be changed.
> parm_name <- c('A','B')
> #
> # Configure alternative method using line number to enter each parameter
> # When line_number is zero, then the input method uses keywords.
> line_number <-c(0,0)
> #
> # Configure each parameter type, where:
> #   1 means a numeric variable informed as a string, such as parm <- "1.38"
> #   2 means a numeric vector informed as a string of numbers separated with a space character.
> #     For example, parm <- "1.25 3.4". You must tell which one will be the variable considered.
> parm_type <- c(1,1)
> #
> # Informe the position of the variable to be considered in the problem in the vector.
> # If the parameter is a numeric variable, then its position is zero.
> parm_vector <- c(0,0)
> #
> # Configure the name of the folder where the command must be called.
> # If the folder is 'wd' then it will not be changed.
> # You can change it to another location where your parameter files are.
> command_folder <- auxi
> #
> # This variable means that the Direct Problem is solved using R or outside
> # if this is FALSE, the results are to be read from a file.
> # When it is TRUE, results will be passed inside R using the variable "results"
> isitR <- TRUE
> #
> # Configure the command to be used to call the Direct Problem Solver.
> command <- 'f1.R'
> #
> # Configure the name of the file to be used as a target by the cost function.
> # The file was built using parm <- c(1,3).
> # It is also a single column of values.
> target <- 'alvo.dat'
> #
> # Configure the name of the folder where the target file can be found.
> # If the folder is 'wd' then it will not be changed.
> # You can change it to another location where your target file is.
> target_folder <- auxi
> #
> # Configure a string to be used to attrib values in the Direct Problem file.
> attrib_str <- '<-'
> #
> # Configure the name of the file with the results obtained by the Direct Problem.
> # It must be a single column of values.
> # The results are changed at each run by the Direct Problem Solver.
> result <- 'result.dat'
> #
> # Configure the name of the folder where the results can be found after each run.
> # If the folder is 'wd' then it will not be changed.
> # You can change it to another location where your result file is.
> result_folder <- tempdir()
> #
> parm<- c(1,3)
> cost(parm)
Warning in file(con, "w") :
  cannot open file 'f1.R': Read-only file system
Error in file(con, "w") : cannot open the connection
Calls: cost -> change_parm -> writeLines -> file
Execution halted