public static void createROC(ClassifierOutput classifierOutput, String filename) {
WriteTextFile out = null;
if (outputROCcsv) {
out = new WriteTextFile(filename.replace(".gif", ".csv"));
out.writeln("FPR,TPR");
}
BufferedImage img = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = (Graphics2D) img.getGraphics();
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setColor(Color.WHITE);
g2d.fillRect(0, 0, width, height);
renderAxes(g2d, 0.2f, 1f);
// renderDiagonal(g2d);
renderROC(g2d, classifierOutput, out);
if (includeAuCinROC) {
double auc =
ClassifierEvaluator.areaUnderCurveConfidenceInterval(classifierOutput).pointEstimate;
g2d.setColor(Color.black);
g2d.setFont(new Font("Arial", Font.PLAIN, 50));
FontMetrics metrics = g2d.getFontMetrics();
String text = "AUC = " + StringUtilities.formatNumber("0.00", auc);
int textWidth = metrics.stringWidth(text);
int textHeight = metrics.getHeight();
g2d.drawString(
text, Math.round(width - textWidth - borderWidth), Math.round(height - textHeight) + 7);
}
try {
ImageIO.write(img, "GIF", new File(filename));
} catch (IOException e) {
e.printStackTrace();
}
if (out != null) out.close();
}
private static void renderROC(
Graphics2D g2d, ClassifierOutput classifierOutput, WriteTextFile out) {
Collections.sort(classifierOutput.scoreLabelPairs);
int postiveCount = countPositives(classifierOutput);
g2d.setColor(new Color(200, 0, 0));
g2d.setStroke(new BasicStroke(4));
float areaWidth = width - 2 * borderWidth;
float areaHeight = height - 2 * borderWidth;
float x = borderWidth;
float y = height - borderWidth;
float previousX = x;
float previousY = y;
double score = classifierOutput.scoreLabelPairs.get(0).score;
int fpCount = 0;
int tpCount = 0;
for (ScoreLabelPair pair : classifierOutput.scoreLabelPairs) {
if (pair.score != score) { // In case of a tie, just make a linear interpolation
g2d.draw(new Line2D.Float(previousX, previousY, x, y));
previousX = x;
previousY = y;
score = pair.score;
}
if (pair.label) tpCount++;
else fpCount++;
float fpr =
(float) fpCount / (float) (classifierOutput.scoreLabelPairs.size() - postiveCount);
float tpr = (float) tpCount / (float) postiveCount;
if (out != null) out.writeln(Float.toString(fpr) + "," + Float.toString(tpr));
x = borderWidth + fpr * areaWidth;
y = height - borderWidth - tpr * areaHeight;
}
g2d.draw(new Line2D.Float(previousX, previousY, x, y));
if (out != null) out.writeln("1,1");
}
