# This program processes data generated by the program write.jl
# It computes the mean values and standard deviations of the mean values
# - separately for data in columns 1 and 2

# This function reads data and computes the means and standard devs

function processdata(f,ftype)
   dd=zeros(Float64,2)                  # to store a single line read from the file
   av=zeros(Float64,2,2)                # to accumulate means and means squares
   fname=string(ftype,"$f",".dat")      # the file name with file index f 
   file=open(fname,"r")
   println(fname)                       # prints the file name as a check
   n=0
   while !eof(file)                     # loop until the end of the file is reached; eof() function
      if ftype=="ran"
         dd[1]=parse(Float64,readuntil(file,"  "))   # reads the number from column 1, assumes "  " item separation
         dd[2]=parse(Float64,readline(file))         # reads the line from column 2
      elseif ftype=="bin"
         read!(file,dd)                              # reads entire 2-number item in binary format
      end 
      @. av[1,:]=av[1,:]+dd[:]          # accumulating the mean
      @. av[2,:]=av[2,:]+dd[:]^2        # accumulating the mean of the squares
      n=n+1                             # counting how many lines processed
   end
   close(file)
   println("Processed lines of data: ",n)    
   @. av[:,:] = av[:,:]/n               # dividing by n to get the mean
   @. av[2,:] = abs((av[2,:]-av[1,:]^2)/(n-1))^0.5    # standard dev of the mean
   return av
end

println("Give file number")   # will read data from one of the files
f=parse(Int,readline(stdin)) 

# The data can be read either from the binary or ASCII formatted file from write.jl

println("ASCII (1) or binary (2) data file")  
t=parse(Int,readline(stdin)) 
if t==1
   ftype="ran"
elseif t==2
   ftype="bin"
else
   throw(DomainError(t,"Follow the instructions, please!"))
end

av=processdata(f,ftype)             # processes the file and obtain the final results

println("Mean values and standard deviations of the mean values")
for i=1:2
   println(i,"  ",av[1,i],"  ",av[2,i])
end