Add working statistics program. Some tradeoffs. Mainly kept simple.

code-clinic/data-gov/Statistics.java

@@ -0,0 +1,173 @@
+import java.util.*;
+import java.io.*;
+
+class Illegal extends IllegalArgumentException {}
+class SuperIllegal extends IllegalArgumentException {
+	public SuperIllegal(String msg){
+		super(msg);
+	}
+}
+
+/** Average - a simple class wrapping a sum and a counter. */
+class Average { 
+	private int n = 0;
+	private int sum = 0;
+	public Average() {}
+	public double addAnother(double s) {
+		sum += s;
+		n++;
+		return (1.0*sum)/n;
+	}
+	public String toString() { return String.format("%.2f",(1.0*sum)/n); }
+	public double getAvg() {
+		return (1.0*sum)/n;
+	}
+	public void resest() { 
+		this.n = 0;
+		this.sum = 0;
+	}
+}
+
+/** Statistics - a static/procedural program for computing statistics from a CSV file. */
+public class Statistics {
+	/* Procedural, static program.
+	 *
+	 * A minimally object-oriented statistics program. 
+	 * This was a final project for my CSC 142 Java Programming 1 students,
+	 * so it was not supposed to be procedural-heavy.
+	 *
+	 * The map collections and Average class are useful in helping
+	 * reduce the number of operations.
+	 */
+	public static void main(String[] args) throws FileNotFoundException, Illegal { 
+
+		System.out.println("\n\nStatistics Program: Alpine Meadows Meteorological Data\n\n");
+
+		// Get stdin scanner
+		Scanner sc = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
+
+		/////////////////////////
+		// I had some abstraction problems up front:
+		// - how much of the problem should be generalized?
+		// - how deep should the object-oriented design go?
+		// - where to stamp out the generality and just get something done?
+		//
+		// Ultimately, my conclusion was,
+		// the top priority is getting it done.
+		// We can pontificate later, and iteratively improve.
+		//
+		// But it is better to quickly solve something that 
+		// really needs a more complicated solution,
+		// than it is to over-complicate a simple problem.
+		////////////////////////
+
+		// Get headers.
+		String[] headers = getHeaders(sc);
+
+		// Extract data by column,
+		// computing a running average as we go.
+		// Ignore first column.
+		Map<String,Average> m = new HashMap<String,Average>();
+		for(int h=0; h<headers.length; h++) { 
+			m.put(headers[h], new Average());
+		}
+
+		// Now run through all the data and compute the running average
+		Average a;
+		while(sc.hasNextLine()) {
+			double[] data = getData(sc, headers.length);
+			// if problems, data.length == 0
+			for(int d=0; d<data.length; d++) { 
+				a = m.get(headers[d]);
+				a.addAnother(data[d]);
+			}
+		}
+
+		// Print a nice fancy report.
+		for(int h=0; h<headers.length; h++) { 
+			System.out.println("Average: "+headers[h] + " = " + m.get(headers[h]));
+		}
+			
+
+	}
+
+	/** Get one row of data from file */
+	public static double[] getData(Scanner sc, int ncols) { 
+
+		double[] data = new double[ncols];
+
+		String line = sc.nextLine();
+		line = scrubComments(line);
+
+		// Now split at ,
+		String[] splitline = line.split(",");
+
+		// Hope this works.
+		// Skip malformed/empty lines
+		if(splitline.length<2) { 
+			// return empty []
+			return data;
+		}
+
+		// Skip first column
+		for(int c=1; c<ncols; c++) { 
+			try { 
+				String token = splitline[c];
+				double d = Double.parseDouble(splitline[c]);
+				data[c] = d;
+
+			} catch(ArrayIndexOutOfBoundsException e) { 
+				continue;
+			}
+		}
+		return data;
+
+	}
+
+	/** Get headers from first row of file */
+	public static String[] getHeaders(Scanner sc) throws Illegal {
+
+		// Read the following from the file:
+		// - column headers
+		int row = 0;
+		while(sc.hasNextLine()) {
+			
+			String line = sc.nextLine();
+			line = scrubComments(line);
+
+			// Now split at ,
+			String[] splitline = line.split(",");
+
+			// Skip malformed/empty lines
+			if(splitline.length<2) { 
+				continue;
+			} else { 
+				return splitline;
+			}
+		}
+		throw new Illegal();
+	}
+
+	/** Scrub comments beginning at # and ending at end of line */
+	public static String scrubComments(String lineIn) {
+		String lineOut = "";
+
+		int commentIndex = -1;
+		for(int j=0; j<lineIn.length(); j++) { 
+			// find the hash sign
+			char c = lineIn.charAt(j);
+			if(c=='#') { 
+				commentIndex = j;
+				break;
+			}
+		}
+		if(commentIndex>=0) {
+			lineOut = lineIn.substring(0,commentIndex);
+		} else {
+			lineOut = lineIn;
+		}
+		return lineOut;
+	}
+
+}
+