R Shiny App error in linear programming: could not find function "lp"?-CodePudding

I am writing my first shiny application where the user enters numeric inputs as vectors, and the output should be the value of the objective function and the values of the final variables. I'm new in shiny and I'm not sure if I have the inputs and function created correctly. Below is the application code:

library(shiny)
library(shinythemes)
library(lpSolveAPI)

ui <- fluidPage(theme = shinytheme("united"),
                navbarPage(" Optimization",
                           tabPanel("Linear programming",
                                    sidebarLayout(
                                      sidebarPanel(
                                        h3('Please enter initial values'),
                                        textInput('obj', 'Objective  function values (comma separated)', "1,2"),
                                        textInput('con', 'ohran vector (comma separated)', "0,1,2,1"),
                                        numericInput('nrow', 'number of rows - constraints', "2"),
                                        textInput('dir', 'Direction - constraints (comma separated)', ">=,<="),
                                        textInput('rhs', 'Right-hand sides - constraint (comma separated)', "2,8"),
                                        submitButton('Submit')
                                      ),
                                      
                                      mainPanel(
                                        h4('The value of the objective function:'),
                                        verbatimTextOutput("value_obj"),
                                        h4('values of variables: '),
                                        verbatimTextOutput("value_var")
            
                                      )
                                  )
                             )
                       )
                )




server <- function(input, output, session) {
  
  
  
  output$value_obj<-renderPrint({
    f.obj <- as.numeric(unlist(strsplit(input$obj,",")))
    f.con <- as.matrix(as.numeric(unlist(strsplit(input$con,","))),nrow=input$nrow, byrow = TRUE )
    f.dir <- as.array(unlist(strsplit(input$dir,",")))
    f.rhs <- as.numeric(unlist(strsplit(input$rhs,",")))
    hodnota_obj = lp("max", f.obj, f.con, f.dir, f.rhs)$objval
       cat("The value of the objective function:\n")
    print(value_obj)
 
  }
  )
  output$value_var<-renderPrint({
    f.obj <- as.numeric(unlist(strsplit(input$obj,",")))
    f.con <- as.matrix(as.numeric(unlist(strsplit(input$con,","))),nrow=input$nrow, byrow = TRUE )
    f.dir <- as.array(unlist(strsplit(input$dir,",")))
    f.rhs <- as.numeric(unlist(strsplit(input$rhs,",")))
    hodnota_obj = lp("max", f.obj, f.con, f.dir, f.rhs)$solution
    cat("The value of the varieaables :\n")
    print(value_var)
    
  }
  )
  

}

# Run the application 
shinyApp(ui = ui, server = server)

CodePudding user response：

The lp function is from lpSolve which is not loaded. In addition, there are some issue in the print statements where it is called print(value_var) or print(value_obj) which is not correct because those objects are not created. The output$value_var and output$value_obj are the output object names created based on the hodnota_obj object

library(shiny)
library(shinythemes)
library(lpSolveAPI)
library(lpSolve)

ui <- fluidPage(theme = shinytheme("united"),
                navbarPage(" Optimization",
                           tabPanel("Linear programming",
                                    sidebarLayout(
                                      sidebarPanel(
                                        h3('Please enter initial values'),
                                        textInput('obj', 'Objective  function values (comma separated)', "1,2"),
                                        textInput('con', 'ohran vector (comma separated)', "0,1,2,1"),
                                        numericInput('nrow', 'number of rows - constraints', "2"),
                                        textInput('dir', 'Direction - constraints (comma separated)', ">=,<="),
                                        textInput('rhs', 'Right-hand sides - constraint (comma separated)', "2,8"),
                                        submitButton('Submit')
                                      ),
                                      
                                      mainPanel(
                                        h4('The value of the objective function:'),
                                        verbatimTextOutput("value_obj"),
                                        h4('values of variables: '),
                                        verbatimTextOutput("value_var")
                                        
                                      )
                                    )
                           )
                )
)




server <- function(input, output, session) {
  
  
  
  output$value_obj<-renderPrint({
    f.obj <- as.numeric(unlist(strsplit(input$obj,",")))
    f.con <- as.matrix(as.numeric(unlist(strsplit(input$con,","))),nrow=input$nrow, byrow = TRUE )
    f.dir <- as.array(unlist(strsplit(input$dir,",")))
    f.rhs <- as.numeric(unlist(strsplit(input$rhs,",")))
    hodnota_obj = lp("max", f.obj, f.con, f.dir, f.rhs)$objval
    cat("The value of the objective function:\n")
    hodnota_obj
   
    
  }
  )
  output$value_var<-renderPrint({
    f.obj <- as.numeric(unlist(strsplit(input$obj,",")))
    f.con <- as.matrix(as.numeric(unlist(strsplit(input$con,","))),nrow=input$nrow, byrow = TRUE )
    f.dir <- as.array(unlist(strsplit(input$dir,",")))
    f.rhs <- as.numeric(unlist(strsplit(input$rhs,",")))
    hodnota_obj = lp("max", f.obj, f.con, f.dir, f.rhs)$solution
    cat("The value of the varieaables :\n")
    hodnota_obj
    
  }
  )
  
  
}

# Run the application 
shinyApp(ui = ui, server = server)

-output