How to get the bars in a bar chart start from the x-axis in java? [closed]

问题

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();

}

回答1:

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

标签

java

eclipse

swing

awt

bar-chart