function Strength = StrengthTime(num)
% This function ->
%       Strength: takes input argument num to which ErrorTime.m,
%       PacketLoss.m, Stats.m, Markov.m and Autocorrelation.m are run
%         If only a single function is wanted, then comment out the
%         corresonding function call.
%          The output of this program will be: 
%           - Total number of `1's and 0's
%           - Loss rate
%           - Markov transitional probabilities
%           - Equilibrium probabilities
%           - eStats for RSSI:Standard_Deviation, Mean and Range
%           - Autocorrelation and written auto'i'
%           - Graphs include:- Time variance of Error rate
%                            - Packet Birst Size
%                            - Time Variance of SIgnal Strength

% NOTE: 
%   - If experiment 4 is not found within the input file, the program
% will output an error
%   - Groups of 10 packets are employed and graphed because plotting
% individual RSSI values against time produced a graph was too compressed
% for visualisation.
%   - The MATLAB program Extract.m has to within the working directory. 
i = 1;
skip = 20;
Subtotal = 0;
SubtotalTime = 0;
group = 1;
room_back = 0;
mp_back = 0;
counter = 1;
found = 0;
error = 0;
line = 0;
times= 0;
format long g
lag = 15; %for autocorrelation (Note: lag of 15 = 30 seconds)
for (i=num:num)
    file = i;
    filename = sprintf('strength%d',file);

    fid = fopen(filename,'r');
    if (fid == -1)
        disp(['ERROR: File not found or could not be opened to read. Please check your input strength file name']);
    end
    
    GROUPSIZE = 10;

    %  Finds exp 5
    while(found < skip)
        tline = fgets(fid);
        line = line + 1; % how many lines scanned
        room = Extract(tline, 1);  % extract room
        mp = Extract(tline, 2);    % extract room

        if (strcmp(tline,'EMPTY'))
            error = error + 1;
            break;
        end

        for (i=1:length(room))
            if (room == room_back) && (mp == mp_back)
                found = found + 1;
                break;
            else
                found = 0;
            end
        end

        room_back = room;
        mp_back = mp;
    end

    % Need to rewind the 19 lines missed
    frewind(fid)
    i = 1;
    line = line - (skip - 1); %skip over the first line

    while(i < line)
        tline = fgets(fid);
        i = i + 1;
    end

    % if no error flagged then run ErrorTime and PacketLoss programs
    if (error ~= 1)
        filename = sprintf('packets%d',file);
        ErrorTime(filename);
        PacketLoss(filename);
        MArkov(filename)
    end

    i = 1; % reset array index
    while(~feof(fid))
        if (error == 1)
            break;
        end

        tline = fgets(fid);
        
        g = sscanf(tline, '%f');            
        tline = tline(13:length(tline));
        time(i) = (g - times);
        RSSI(i) = Extract(tline, 7);
        times = g;
        
        Subtotal = (Subtotal + (RSSI(i)-256));
        SubtotalTime = SubtotalTime + time(i);

        if (rem(i,GROUPSIZE)==0)
            Strength(group) = (Subtotal/GROUPSIZE);
            Time(group) = (SubtotalTime);
            SubtotalTime = 0;
            Subtotal = 0;            
            group = group + 1;
        end
        i = i + 1;
    end

    fclose(fid);

    if (error ~= 1)
        Stats(Strength, RSSI, GROUPSIZE, Time)
    end

    %calculate autocorrelatioan and write to file
    Autocorrelation(file, RSSI, lag) 
    
end