Develop Reference

I am Using Mp Chart android I want yAxis values as showing in a red circle

YAxis leftAxis1 = barChart.getAxisLeft();
leftAxis1.setDrawLabels(true);
leftAxis1.setDrawAxisLine(false);
leftAxis1.setDrawGridLines(true);
leftAxis1.setEnabled(true);
leftAxis1.setDrawZeroLine(true);
//leftAxis1.setTypeface(); // set a different font
leftAxis1.setTextSize(12f); // set the text size
leftAxis1.setAxisMinimum(0f); // start at zero
leftAxis1.setAxisMaximum(100f); // the axis maximum is 100
leftAxis1.setTextColor(Color.BLACK);
leftAxis1.setValueFormatter(new MyValueFormatter());
leftAxis1.setGranularity(1f); // interval 1
leftAxis1.setLabelCount(9, true);
//leftAxis1.setDrawZeroLine(true);
YAxis rightAxis1 = barChart.getAxisRight();
rightAxis1.setEnabled(false);
}
private class MyValueFormatter implements IAxisValueFormatter {
private DecimalFormat mFormat;
public MyValueFormatter() {
mFormat = new DecimalFormat("###,###,##0.0"); // use one decimal
}
#Override
public String getFormattedValue(float value, AxisBase axis) {
return mFormat.format(value) + " $"; // e.g. append a dollar-sign
}
}
}
I want to have my graph's y-axis values similar to the ones shown in the above image. How would I make it like that? There should be intervals of 10 between for the y-values. Is there any way to do this?

This should help you:
mChart.getAxisLeft().setGranularity(10);
It will make Y axis values increase by 10 and you will have desired result. Howerever, if you zoomin, the values and graph will be changed (it is normal). If you also want to disable zooming in and out you can disable it :
mChart.setScaleEnabled(false);
Hope that helps

Set
rightAxis1.setEnabled(false);
to
rightAxis1.setEnabled(true);

Show XY Plot with only one value in Androidplot

I am using Androidplot to display real time data. The real time data is dynamic and the x axis is time. The domain is a fixed timespan. Because the values could be any double, rangeStepMode is set to subdivide the y-axis. The issue is that when all the values are the same, the plot does not draw correctly.
You can see in the image that there are no range grids or labels.
From this related question:
This happens because Androidplot does not have enough information to automatically calculate what a reasonable domain/range scale would be from a single point.
This makes sense, and the linked solution of setting a non-zero range boundary works but instead of an arbitrary range like miny - 1to maxy + 1, I'd like for there to be only one labeled range line in these cases across the middle of the screen.
My Activity:
public class SimpleXYPlotActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.simple_xy_plot_example);
XYPlot plot = (XYPlot) findViewById(R.id.plot);
Number[] series1Numbers = new Number[]{
1,
1,
};
XYSeries series1 = new SimpleXYSeries(SimpleXYSeries.ArrayFormat.Y_VALS_ONLY, "Series1", series1Numbers);
LineAndPointFormatter series1Format = new LineAndPointFormatter(Color.RED, Color.GREEN, null, null);
plot.addSeries(series1, series1Format);
StepMode stepMode = StepMode.SUBDIVIDE;
int stepValue = 10;
plot.setRangeStepMode(stepMode);
plot.setRangeStepValue(stepValue);
}
}
My Layout:
<com.androidplot.xy.XYPlot
android:id="#+id/plot"
style="#style/APDefacto.Dark"
android:layout_width="match_parent"
android:layout_height="match_parent"
ap:rangeStep="5"
ap:rangeStepMode="subdivide"
ap:domainStep="1"
ap:domainStepMode="increment_by_val"
/>
What I've tried
The following works on the simple xy example, but when I try setting it within minmax in my time series class, the thread drawing the domain gridlines gets into a very long loop as it calculates xPix to be very very large. This also isn't a very solution for situations where I have multiple series. Any ideas on how I can get the results I want?
Double minY = null;
Double maxY = null;
for (Double aDouble : series1Numbers) {
if (minY == null) {
minY = aDouble;
} else {
minY = Math.min(minY, aDouble);
}
if (maxY == null) {
maxY = aDouble;
} else {
maxY = Math.max(maxY, aDouble);
}
}
if (minY.equals(maxY)) {
plot.setUserRangeOrigin(minY);
plot.setRangeBoundaries(0, 2 * maxY, BoundaryMode.FIXED);
plot.setRangeStepMode(StepMode.INCREMENT_BY_PIXELS);
plot.setRangeStepValue(Double.POSITIVE_INFINITY);
} else {
plot.setUserRangeOrigin(0);
plot.setRangeBoundaries(minY, maxY, BoundaryMode.FIXED);
plot.setRangeStepMode(StepMode.SUBDIVIDE);
plot.setRangeStepValue(5);
}

This wont get rid of the CPU overhead but you can use PlotUtils.minMax to find these values for you
If implementing and using FastXYSeries is a possibility for you then the overhead of using minMax drops away too, as the calculation only ever gets done when your XYSeries data changes.

Vertical orientation degree - Android

Anyone knows how to get smooth vertical orientation degree in Android?
I already tried OrientationEventListener as shown below but it's very noisy. already tried all rates, Normal, Delay, Game and Fastest, all shown the same result.
myOrientationEventListener = new OrientationEventListener(this, SensorManager.SENSOR_DELAY_NORMAL) {
#Override
public void onOrientationChanged(int arg0) {
orientaion = arg0;
Log.i("orientaion", "orientaion:" + orientaion);
}
};

So there are two things going on that can affect what you need.
Sensor delay. Android provides four different sensor delay modes: SENSOR_DELAY_UI, SENSOR_DELAY_NORMAL, SENSOR_DELAY_GAME, and SENSOR_DELAY_FASTEST, where SENSOR_DELAY_UI has the longest interval between two data points and SENSOR_DELAY_FASTEST has the shortest. The shorter the interval the higher data sampling rate (number of samples per second). Higher sampling rate gives you more "responsive" data, but comes with greater noise, while lower sampling rate gives you more "laggy" data, but more smooth.
Noise filtering. With the above in mind, you need to decide which route you want to take. Does your application need fast response? If it does, you probably want to choose a higher sampling rate. Does your application need smooth data? I guess this is obviously YES given the context of the question, which means you need noise filtering. For sensor data, noise is mostly high frequency in nature (noise value oscillates very fast with time). So a low pass filter (LPF) is generally adequate.
A simple way to implement LPF is exponential smoothing. To integrate with your code:
int orientation = <init value>;
float update_rate = <value between 0 to 1>;
myOrientationEventListener = new OrientationEventListener(this, SensorManager.SENSOR_DELAY_NORMAL) {
#Override
public void onOrientationChanged(int arg0) {
orientation = (int)(orientation * (1f - update_rate) + arg0 * update_rate);
Log.i("orientation", "orientation:" + orientation);
}
};
Larger update_value means the resulting data is less smooth, which should be intuitive: if update_value == 1f, it falls back to your original code. Another note about update_value is it depends on the time interval between updates (related to sensor delay modes). You probably can tune this value to find one works for you, but if you want to know exactly how it works, check the alpha value definition under Electronic low-pass filters -> Discrete-time realization.

I had a similar problem showing an artificial horizon on my device. The low pass filter (LPF) solved this issue.
However you need to consider when you use the orientation angle in degrees and apply the LPF on it blindly, the result is faulty when the device is in portrait mode and turned from left to ride or opposite. The reason for this is the shift between 359 and 0 degree. Therefore I recommend to convert the degree into radians and apply the LPF on the sin and cos values of the orientation angle.
Further I recommend to use a dynamic alpha or update rate for the LPF. A static value for the alpha might be perfect on your device but not on any other.
The following class filters based on radians and uses a dynamic alpha as described above:
import static java.lang.Math.*;
Filter {
private static final float TIME_CONSTANT = .297f;
private static final float NANOS = 1000000000.0f;
private static final int MAX = 360;
private double alpha;
private float timestamp;
private float timestampOld;
private int count;
private int values[];
Filter() {
timestamp = System.nanoTime();
timestampOld = System.nanoTime();
values = new int[0];
}
int filter(int input) {
//there is no need to filter if we have only one
if(values.length == 0) {
values = new int[] {0, input};
return input;
}
//filter based on last element from array and input
int filtered = filter(values[1], input);
//new array based on previous result and filter
values = new int[] {values[1], filtered};
return filtered;
}
private int filter(int previous, int current) {
calculateAlpha();
//convert to radians
double radPrev = toRadians(previous);
double radCurrent = toRadians(current);
//filter based on sin & cos
double sumSin = filter(sin(radPrev), sin(radCurrent));
double sumCos = filter(cos(radPrev), cos(radCurrent));
//calculate result angle
double radRes = atan2(sumSin, sumCos);
//convert radians to degree, round it and normalize (modulo of 360)
long round = round(toDegrees(radRes));
return (int) ((MAX + round) % MAX);
}
//dynamic alpha
private void calculateAlpha() {
timestamp = System.nanoTime();
float diff = timestamp - timestampOld;
double dt = 1 / (count / (diff / NANOS));
count++;
alpha = dt/(TIME_CONSTANT + dt);
}
private double filter(double previous, double current) {
return (previous + alpha * (current - previous));
}
}
For further readings see this discussion.

MPAndroid - snapping x position when scrolling

After few hours of trying I'm looking for some hints on how to add snap-scroll mechanism to MPAndroid. Basically I want the 5 visible bars to align so they are fully visible and centered. I now imported the library source code because it looks like there's no other way to change the code in computeScroll (BarLineChartTouchListener).
Edit:
To clarify - I'm showing around 20 bars but chart is zoomed so user can scroll horizontally. What bothers me it is not getting aligned automatically so first visible bar might be clipped in half. I'm looking for snapping effect where it will round the position to the nearest multiplication of the bar width, leaving 5 fully visible bars.

I ended up adding the following function in BarLineChartBase.java. I know it's far from elegant, but seems to do the job. It's limited to targetApi > 11, because of the ValueAnimator. For lower API (which I don't cater for) you might need to have a look at nineoldandroids or some other animation loop technique.
#TargetApi(Build.VERSION_CODES.HONEYCOMB)
public void alignX() {
int count = this.getValueCount();
int xIndex = this.getLowestVisibleXIndex() + Math.round( (this.getHighestVisibleXIndex() - this.getLowestVisibleXIndex()) / 2.0f );
float xsInView = this.getXAxis().getValues().size() / this.getViewPortHandler().getScaleX();
Transformer mTrans = this.getTransformer(YAxis.AxisDependency.LEFT);
float[] pts = new float[] { xIndex - xsInView / 2f, 0 };
mTrans.pointValuesToPixel(pts);
final Matrix save = new Matrix();
save.set(this.getViewPortHandler().getMatrixTouch());
final float x = pts[0] - this.getViewPortHandler().offsetLeft();
final int frames = 20;
ValueAnimator valueAnimator = new ValueAnimator().ofInt(0, frames);
valueAnimator.setDuration(500);
valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
int prev = -1;
#Override
public void onAnimationUpdate(ValueAnimator animation) {
if( (int) animation.getAnimatedValue() > prev ) {
save.postTranslate( -x / (float)frames, 0);
BarLineChartBase.this.getViewPortHandler().refresh(save, BarLineChartBase.this, true);
}
prev = (int) animation.getAnimatedValue();
}
});
valueAnimator.start();
}
I trigger it at the end of computeScroll function in BarLineChartTouchListener.
I kept names of variables as I copied code from functions like MoveViewJob, ViewPortHandler etc. Since it's only aligning in x axis - I removed Y axis calculations and used zeros instead. Any optimizations welcome, especially from the author #PhilippJahoda.

AChartEngine max x labels visible

My question is how to set in AChartEngine lots of x labels on x axis and set visible only for example 20 and when make zoom in more precision labels will appear.

At the beginning, just set the needed maximum number of labels for the initial view:
renderer.setXLabels(20);
Whenever you zoom in, AChartEngine will update the labels to have a maximum number of 20 labels. It automatically chooses the round values labels, so you won't have exactly 20, but you will have a decent number of quite round numbers.
On the other side, if you mean custom text labels, like the ones you add using renderer.setXTextLabel() then you have to listen for zoom events and update the labels accordingly:
mChartView.addZoomListener(new ZoomListener() {
public void zoomApplied(ZoomEvent e) {
double start = renderer.getXAxisMin();
double stop = renderer.getXAxisMax();
double step = (stop - start) / 20;
renderer.removeXTextLabels();
for (double i = start; i <= stop; i += step) {
renderer.addXTextLabel(i, "text");
}
}
public void zoomReset() {
}
}, true, true);