Keeping track of my calories the R way

require("Rook")
library("lubridate")
setwd("C:/Blag/R_Scripts")

Blag_Fitness = read.csv(file="Blag_Fitness.csv",header=TRUE)
Blag_Fitness$Date<-strptime(Blag_Fitness$Date,"%d/%m/%Y")
Rows<-nrow(Blag_Fitness)
Rows
Default_Day<-day(Blag_Fitness$Date[1])
Default_Month<-month(Blag_Fitness$Date[1])
Default_Last_Day<-day(Blag_Fitness$Date[Rows])
Default_Last_Day
Default_Last_Month<-month(Blag_Fitness$Date[Rows])

fill_zeros<-function(param,mode=0){
    count<-nchar(param)
    zeros<-rep(0,1)
    if(mode==0){
      if(count==1){
        r_param<-c(zeros,param)
      }else{
        r_param<-c(param)
      }
    }else{
      if(count==7){
        r_param<-c(zeros,param)
      }else{
        r_param<-c(param)
      }      
    }
    r_param<-paste(r_param,collapse="")
    return(r_param)      
}

newapp<-function(env){
  req<-Rook::Request$new(env)
  res<-Rook::Response$new()
  
  res$write('<form method="POST">\n')
  res$write('<div align="center"><table><tr>') 
  res$write('<td><select name=DAYFROM>')
  for(i in 1:31) {
    if(i==Default_Day){
      res$write(sprintf('<OPTION VALUE=%s SELECTED=%s>%s</OPTION>',
                        i,Default_Day,i))
    }else{
      res$write(sprintf('<OPTION VALUE=%s>%s</OPTION>',i,i))
    }
  }
  res$write('</select></td><td>')
  res$write('<select name=MONTHFROM>')
  for(i in 1:12) {
    if(i==Default_Month){
      res$write(sprintf('<OPTION VALUE=%s SELECTED=%s>%s</OPTION>',
                        i,Default_Month,i))
    }else{
      res$write(sprintf('<OPTION VALUE=%s>%s</OPTION>',i,i))
    }
  }
  res$write('</select></td>')
  res$write('</select></td><td>')
  res$write('<select name=YEARFROM>')
  for(i in 2012:2020) {
    res$write(sprintf('<OPTION VALUE=%s>%s</OPTION>',i,i))
  }
  
  res$write('</select></td>')
  res$write('<td>To</td>')

  res$write('<td><select name=DAYTO>')
  for(i in 1:31) {
    if(i==Default_Last_Day){
      res$write(sprintf('<OPTION VALUE=%s SELECTED=%s>%s</OPTION>',
                        i,Default_Last_Day,i))
    }else{
      res$write(sprintf('<OPTION VALUE=%s>%s</OPTION>',i,i))
    }
  }
  res$write('</select></td><td>')
  res$write('<select name=MONTHTO>')
  for(i in 1:12) {
    if(i==Default_Last_Month){
      res$write(sprintf('<OPTION VALUE=%s SELECTED=%s>%s</OPTION>',
                        i,Default_Last_Month,i))
    }else{
      res$write(sprintf('<OPTION VALUE=%s>%s</OPTION>',i,i))
    }
  }
  res$write('</select></td>')
  res$write('</select></td><td>')
  res$write('<select name=YEARTO>')
  for(i in 2012:2020) {
    res$write(sprintf('<OPTION VALUE=%s>%s</OPTION>',i,i))
  }
  res$write('</select></td>')  
  
  res$write('<td><input type="submit" value="Get Stats"></td>')
  res$write('</tr></table></div>')
  res$write('</form>')
  
  if (!is.null(req$POST())) {
    p_dayfrom = req$POST()[["DAYFROM"]]
    p_monthfrom = req$POST()[["MONTHFROM"]]
    p_yearfrom = req$POST()[["YEARFROM"]]
    p_dayto = req$POST()[["DAYTO"]]
    p_monthto = req$POST()[["MONTHTO"]]
    p_yearto = req$POST()[["YEARTO"]]
    p_dayfrom<-fill_zeros(p_dayfrom)
    p_monthfrom<-fill_zeros(p_monthfrom)
    date_from<-c(p_dayfrom,'/',p_monthfrom,'/',p_yearfrom)
    date_from<-paste(date_from,collapse="")
    date_from_n<-strptime(date_from,"%d/%m/%Y")
    date_from_n<-as.numeric(format(date_from_n,"%d%m%Y"))
    p_dayto<-fill_zeros(p_dayto)
    p_monthto<-fill_zeros(p_monthto)
    date_to<-c(p_dayto,'/',p_monthto,'/',p_yearto)
    date_to<-paste(date_to,collapse="")
    date_to_n<-strptime(date_to,"%d/%m/%Y")
    date_to_n<-as.numeric(format(date_to_n,"%d%m%Y"))
    
    Blag_Fitness$Date<-as.numeric(format(Blag_Fitness$Date,"%d%m%Y"))
    
    Selected_Data<-subset(Blag_Fitness, Date >= date_from_n & Date <= date_to_n)
    Selected_Data$Date<-as.character(Selected_Data$Date)
    fixer<-fill_zeros
    Selected_Data$Date<-sapply(Selected_Data$Date,fixer,mode=1)
    Selected_Data$Date<-strptime(Selected_Data$Date,"%d%m%Y")

    res$write(sprintf('<div align="center"><h3>From %s to %s</h3></div>',
                      date_from,date_to))
    
    png("Blag_Fitness.png",width=800,height=500)
    plot(Selected_Data,type="n")
    lines(Selected_Data,col="blue",ann=FALSE)
    points(Selected_Data, pch=21, bg="lightcyan", cex=1.25)
    dev.off()
    res$write("<div align='center'>")
    res$write(paste("<img src='", server$full_url("pic"), "/", 
                    "Blag_Fitness.png'", "/>", sep = ""))
    
    res$write("</div>")    
  }else{
    res$write("<p>No data to select...</p>")
  }
  res$finish()
}

server = Rhttpd$new()
server$add(app = newapp, name = "Blag_Fitness")
server$add(app = File$new("C:/Blag/R_Scripts"), name = "pic")
server$start()
server$browse("Blag_Fitness")