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

Question

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();

}

Ybarra

Didn't you ask this same question in the last 48 hours? I seem to recall giving the advice: For better help sooner, post a minimal reproducible example or Short, Self Contained, Correct Example. – Housemother

Use a logical and consistent form of indenting code lines and blocks. The indentation is intended to make the flow of the code easier to follow! – Housemother

I am just trying to get the idea of positioning the bar. How do you normally position a bar on the x-axis? – Ybarra

How do I fix it so that it starts from the x-axis line.- you use basic math. We have no idea what your variables mean, so you need to do the math yourself. You need to know the "y offset" value of the "X Axis" line. Then you need to know the height of the bar. Then instead of drawing the rectangle below the "X Axis" line you want to draw it above, so the "y value" is equal to the "X Axis" y offset minus the height of the bar. – Connatural

"I am just trying to get the idea of positioning the bar." That does not answer my question. Please answer the question. – Housemother

I have posted the code now. Sorry for not doing it earlier. – Ybarra

} catch (Exception e) { } Never do that. Instead change it to (at least, short of a proper logging implementation) } catch (Exception e) { e.printStackTrace(); // remove head from sand.. } – Housemother

As an aside, the uncompilable code snippet that is an MCVE/SSCCE as I suggested. Do yourself a favour and actually read both documents. – Housemother

"For once.." Don't mistake your personal experience for how I typically interact with people. You're 'special' (by your own actions). – Housemother

Answer 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.

Pen

thank you sir. can you please share the code used for the fillRect? Because I am having trouble understanding the variables without its values. – Ybarra

I've elaborated above; if your fragment is from an implementation of paintComponent(), don't call repaint() recursively. – Pen

Thanks a lot sir. At least someone is helping with meaningful answers :) – Ybarra

See also this related example. – Pen

......................Sweet! – Rutan