%Tutorial 1 - CBE 20258 Computer Methods
 
echo on
clc; 
clear;

%The following two commands are used to import
%data from excel spreadsheet. This is analogous
%to the procedure explained in the online tutorial
%Importing data from excel spreadsheets...
sp500=xlsread('sp500.xls',1,'','basic');
sp500e=xlsread('sp500_energy.xls',1,'','basic');
pause;

%Note that if the file was in the appropriate directory (workspace)
%you could have double-clicked on it.  The "clear" command would
%have wiped it out, though, so it often makes sense to explicitly
%load the file too.
pause;

%The subplot command creates a set of plots in the same figure
%Subplot(1,2,1) means the figure has 1 row and 2 columns of plots. 
%The third argument means that the first plot will be specified

figure(1)
subplot(1,2,1)
plot(sp500(:,1),sp500(:,2));

%Datetick command writes the X axis in Date format.
%There are 17 formats available, you can take a look at them by 
%typing 'help datetick' on the command window.

datetick('x',12);
xlabel('Date')
ylabel('S&P 500 Fund Price (USD)')

%Now the second plot will be specified

subplot(1,2,2)
plot(sp500e(:,1),sp500e(:,2)); 
datetick('x',12);
xlabel('Date')
ylabel('S&P 500 Energy Fund Price (USD)')
pause;

%Concatenate two arrays: 
%The first column has the dates
%The second column the S&P 500 data
%The third column has the S&P Energy 500 data

funds = [sp500(:,1), sp500(:,2), sp500e(:,2)];

%Plot this in a different figure

figure(2)
plot(funds(:,1),funds(:,2),funds(:,1),funds(:,3));
datetick('x',12); 
xlabel('Date')
ylabel('Fund Price(USD)')
legend('S&P 500','S&P 500 Energy')

pause;

%Extract the first 250 hundred days data from S&P

first250=[1:250];
first_250_days_sp500 = [sp500(first250,:)];

%Plot them..."
figure(3)
plot(first_250_days_sp500(:,1), first_250_days_sp500(:,2))
datetick('x',12);
title('First 250 days of the S&P 500 Fund price')
xlabel('Date')
ylabel('Fund Price (USD)')
pause;

%Save them into the file "first_days.mat"
save('first_days','first_250_days_sp500')
%Load the first 250 days data back again
load('first_days.mat');
pause;

%We can use the data we just extracted to figure out when the minimum
%and maximum prices of this stock occurred.

%The max function returns two results, the maximum number found in a vector
%and its index within this vector. The max function can also be used in
%the following way

%max(vector)

%This would only return the maximum value, no index. Type help max for more
%info

[max_price,index_max] = max(first_250_days_sp500(:,2));
[min_price,index_min] = min(first_250_days_sp500(:,2));

difference = max_price - min_price;
yield = difference*100/min_price;

%Datestr works similarly to datetick. Type help datestr for more info.
when_to_buy = datestr(first_250_days_sp500(index_min,1),2);
when_to_sell = datestr(first_250_days_sp500(index_max,1),2);

echo off
%Display data in the command line
text_string=['The maximum price of the S&P fund was ', num2str(max_price), ' USD'];
disp(text_string)
text_string=['The minimum price of the S&P fund was ', num2str(min_price), ' USD'];
disp(text_string)
text_string=['The optimum buying time is ', when_to_buy,'. The optimum selling time is ', when_to_sell];
disp(text_string)
text_string=['The inversion yield is ',num2str(yield),'%'];
disp(text_string)