WeatherGenerator.java

/*
 *
 * To generate weather for location at longitude -98.76 and latitude 26.70 for
 * the month of February do:
 * java WeatherGenerator -98.76 26.70 3
 * 
 * Remember that January is 2, February is 3 and so on.
 */
 

public class WeatherGenerator {

    static final int WET = 1; // Use this value for a wet day
    static final int DRY = 2; // Use this value for a dry day 
    
    // Number of days in each month, January is index 0, February is index 1
    static final int[] numberOfDaysInMonth = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

    /*
     * Given a location (longitude, latitude) in the USA and a month of the year, the method
     * returns the forecast for the month based on the drywet and wetwet transition 
     * probabilities tables.
     * 
     * month will be a value between 2 and 13: 2 corresponds to January, 3 corresponds to February
     * and so on. These are the column indexes of each month in the transition probabilities tables.
     * 
     * The first day of the month has a 50% chance to be a wet day, 0-0.49 (wet), 0.50-0.99 (dry)
     * 
     * Use StdRandom.uniform() to generate a real number uniformly in [0,1)
     * 
     */
    public static int[] oneMonthGenerator(double longitute, double latitude, 
    int month, double[][] drywet, double[][] wetwet) {

        // WRITE YOUR CODE HERE
        int counter = 0;
   
        for(int i = 0; i < drywet.length;i++)
        {
            
            if((drywet[i][0] == longitute) && (drywet[i][1] == latitude))
            {
                counter = i;
                break;
            } 
    
        }
        int[] w = new int[numberOfDaysInMonth[month-2]];
        
        
        boolean iswet = false;
        if(StdRandom.uniform() <= .49)
        {
            iswet = true;
            w[0] = 1;
        }
        else
        {
            w[0] = 2;
        }

        for(int i = 1;i < w.length;i++)
        {
            if(iswet == true)
            {
                if(StdRandom.uniform() <= wetwet[counter][month])
                {
                    iswet = true;
                }
                else
                {
                    iswet = false;
                }
            }
            else
            {
                if(StdRandom.uniform() <= drywet[counter][month])
                {
                    iswet = true;
                }
                else
                {
                    iswet = false;
                }
            }

            int n = 1;
            if(iswet == true)
            {
                n = 1;
            }
            else if(iswet == false)
            {
                n = 2;
            }
            w[i] = n;
        }    
        return(w);
    }

    /*
     * Returns the number of mode (WET or DRY) days in forecast.
     */ 
    public static int numberOfWetDryDays (int[] forecast, int mode) {
        
        // WRITE YOUR CODE HERE
        int counter = 0;
        for(int i = 0; i < forecast.length; i++)
        {
            if(forecast[i] == mode)
                counter++;
        }
        return(counter);
    }

    /*
     * Returns the longest number of consecutive mode (WET or DRY) days in forecast.
     */ 
    public static int lengthOfLongestSpell (int[] forecast, int mode) {

        // WRITE YOUR CODE HERE
        int counter = 0;
        int streak = 0;
        for(int i = 0; i < forecast.length; i++)
        {
            if(forecast[i] == mode)
                counter++;
            else
                counter = 0; 
            if(counter > streak)
            {
                streak = counter;
            }
            
        }
        return(streak);
    }

    /*
     * Reads numberOfLocations probabilites into arrayToFill.
     * 
     * Transition probabilities file format:
     * Longitude	Latitude	January	February	March	April	May	June	July	August	September	October	November	December 
     * -97.58	    26.02	    0.76	0.75	    0.77	0.74	0.80	0.86	0.94	0.97	0.89	0.77	0.74	0.77
     */ 
    public static void readTransitionProbabilities ( double[][] arrayToFill, 
    int numberOfLocations ) {
        int row = 0;
        while (row < numberOfLocations) {
            arrayToFill[row][0] = StdIn.readDouble();  // Longitute
            arrayToFill[row][1] = StdIn.readDouble();  // Latitude
            arrayToFill[row][2] = StdIn.readDouble();  // January
            arrayToFill[row][3] = StdIn.readDouble();  // February
            arrayToFill[row][4] = StdIn.readDouble();  // March
            arrayToFill[row][5] = StdIn.readDouble();  // April
            arrayToFill[row][6] = StdIn.readDouble();  // May
            arrayToFill[row][7] = StdIn.readDouble();  // June
            arrayToFill[row][8] = StdIn.readDouble();  // July
            arrayToFill[row][9] = StdIn.readDouble();  // August
            arrayToFill[row][10] = StdIn.readDouble(); // Septmber
            arrayToFill[row][11] = StdIn.readDouble(); // October
            arrayToFill[row][12] = StdIn.readDouble(); // November
            arrayToFill[row][13] = StdIn.readDouble(); // December
            row += 1;
        }
    }

    /*
     *
     * Expects files in the same directory. The first (drywet.txt) contains
     * transition probabilities that reflects how often the weather changes
     * from wet to dry. The second (wetwet.txt) is transition probabilities
     * that reflects that the weather remains wet from one day to the next.
     * 
     */
    public static void populateTransitionProbabilitiesArrays(double[][] drywet, 
    double[][] wetwet, int numberOfLocations) {

        // Read transition probabilities that reflects how often the weather
        // changes from wet to dry into 2D array drywet.
        // The first line on the file has number of locations (lines)
        StdIn.setFile("drywet.txt");
        readTransitionProbabilities(drywet, numberOfLocations);

        // Read transition probabilities that reflects that the weather remains 
        // wet from one day to the next into 2D array wetwet.
        // The first line on the file has number of locations (lines)
        StdIn.setFile("wetwet.txt");
        readTransitionProbabilities(wetwet, numberOfLocations);
    }

    /*
     *
     * Reads the files containing the transition probabilities for US locations.
     * 
     * To find 
     * 
     * Execution:
     *   java WeatherGenerator -97.58 26.02 3
     * 
     * 
     */

    public static void main (String[] args) {
        
        int numberOfRows    = 4001; // Total number of locations
        int numberOfColumns = 14;   // Total number of 14 columns in file 
                                    // File format: longitude, latitude, 12 months of transition probabilities
        
        // Allocate and populate arrays that hold the transition probabilities
        double[][] drywet = new double[numberOfRows][numberOfColumns];
        double[][] wetwet = new double[numberOfRows][numberOfColumns];
        populateTransitionProbabilitiesArrays(drywet, wetwet, numberOfRows);

        /*** WRITE YOUR CODE BELLOW THIS LINE. DO NOT erase any of the lines above. ***/

        // Read command line inputs 
        double longitute = Double.parseDouble(args[0]);
        double latitude  = Double.parseDouble(args[1]);
        int    month     = Integer.parseInt(args[2]);

        int[] forecast = oneMonthGenerator(longitute, latitude, month, drywet, wetwet);
        int drySpell = lengthOfLongestSpell(forecast, DRY);
        int wetSpell = lengthOfLongestSpell(forecast, WET);

        StdOut.println("There are " + forecast.length + " days in the forecast for month " + month);
        StdOut.println(drySpell + " days of dry spell.");

        for ( int i = 0; i < forecast.length; i++ ) {

            // This is the ternary operator. (conditional) ? executed if true : executed if false
            String weather = (forecast[i] == WET) ? "Wet" : "Dry";  
            StdOut.println("Day " + (i+1) + " is forecasted to be " + weather);
        }
    }
}