As you can see in the picture, the bars in the chart starts below the x-axis. How do I fix it so that it starts from the x-axis line? Please suggest me a fix and also I would be helpful to know where I am going wrong.
private int PAD = 20;
private int LPAD = 35;
private int DPAD = 25;
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.BLACK);
String DataString[] = dataset.split(", ");
double DataArray[] = new double[DataString.length];
double MaxValue = 0;
int w = getWidth();
int h = getHeight();
for (int i = 0; i < DataString.length; i = i + 1) {
try {
double out = Double.parseDouble(DataString[i]);
DataArray[i] = out;
if (out > MaxValue) {
MaxValue = out;
}
} catch (NumberFormatException e) {
}
}
double xScale = (w - 1 * (PAD + LPAD)) / (DataArray.length) - 1;
double yScale = (h - 3 * DPAD) / MaxValue;
// The initial x,y (0).
int x0 = LPAD;
try {
if (DataArray.length > 1) {
// Draw Graph
g2.drawLine(PAD + LPAD, PAD, PAD + LPAD, h - (PAD + LPAD));
g2.drawLine(PAD + LPAD, h - PAD - LPAD, x0 + (int) (DataArray.length * xScale), h - (PAD + LPAD));
Color cd = new Color(135, 90, 185);
g2.setPaint(cd);
g2.drawString(title, w / 4, padding - 15);
g2.drawString(xAxis, w / 2 - padding, h - (padding - 10));
g2.rotate(Math.toRadians(270));
g2.drawString(yAxis, -(h / 2 + padding) - LPAD, PAD - 5);
g2.rotate(-Math.toRadians(270));
g2.setPaint(Color.BLACK);
double intin = Double.parseDouble(interval);
double sin = Double.parseDouble(start);
for (int j = 0; j < DataArray.length; j++) {
int x1 = x0 + (int) (j * xScale) + PAD;
double y1 = (int) ((MaxValue - DataArray[j]) * yScale + PAD) - 2;
// g2.drawLine(x1-3, (int) y1-3, x1+3, (int) y1+3);
// g2.drawLine(x1-3,(int) y1+3,x1+3,(int) y1-3);
// g2.drawLine(x1, h - (PAD + LPAD), x1, h - (PAD +
// LPAD)+5);
double intout = (sin + (intin * j));
String interval = String.valueOf(intout);
g2.drawString(interval, x1, h - LPAD);
}
for (int i = 0; i < 9; i++) {
int x3 = PAD + LPAD;
int x1 = x3 - 5;
int y0 = (h - (PAD)) - (((i + 1) * (h - PAD * 3)) / 10 + DPAD) - 2;
int y3 = y0;
g2.drawLine(x3, y0, x1, y3);
}
// g2.drawLine(PAD + LPAD, h - (PAD + LPAD), PAD + LPAD - 5,
// h - (PAD + LPAD));
g2.drawLine(PAD + LPAD, PAD, PAD + LPAD - 5, PAD);
g2.drawString(start, LPAD - 20, h - (LPAD) - 20);
Long L = Math.round(MaxValue);
int MVi = Integer.valueOf(L.intValue());
String MVstring = String.valueOf(MVi);
int MVmid = MVi / 2;
String MVmidstring = String.valueOf(MVmid);
g2.drawString(MVmidstring, PAD, (h - PAD) / 2);
g2.drawString(MVstring, PAD, PAD);
g2.setColor(Color.red);
for (int j = 0; j < DataArray.length; j++) {
int x1 = x0 + (int) (j * xScale) + PAD;
double y1 = (int) ((MaxValue - DataArray[j]) * yScale + PAD) - 2;
g2.fillRect(x1 + 2, (int) y1 + 1 , w - (PAD * 42), h);
}
}
} catch (Exception e) {
}
}
repaint();
}
How do you normally position a bar over the x-axis?
A bar's fillRect() parameters should be left, top, width and height. Focusing on just the vertical size and position, as shown here, you can scale the bar height to the plot area height using a proportion:
barHeightInPixels : plotHeightInPixels :: value : maxDataValue
Solving for barHeightInPixels,
panelHeightInPixels = panel.getHeight();
plotHeightInPixels = panelHeightInPixels - axisOffset;
barHeightInPixels = value * plotHeightInPixels / maxDataValue;
Now use the scaled height:
g2.fillRect(
barCenter - (barWidth / 2), //left
panelHeightInPixels - barHeightInPixels - axisOffset, //top
barWidth, //width
barHeightInPixels); //height
To see how additional features are implemented, study the code provided by a chart library, as suggested in this answer to your previous question on this topic.
来源：https://stackoverflow.com/questions/36961784/how-to-get-the-bars-in-a-bar-chart-start-from-the-x-axis-in-java