I have tried to see if I can do this on AndroidPlot, HelloCharts and MPAndroidChart. I have a Weight Management App and want to show a chart of how weight has changed over time.
I've just started looking at this and am falling at the first hurdle of plotting irregular intervals on the X axis. All of the examples for all of these seem to show linear plotting with every interval on the X axis having a value plotted.
But my users might weigh themselves everyday for a week and then wait a month before the next weight so there should be a linear date scale and weights mapped against it but with many days not having a value to plot.
Am i missing something obvious or is this something that these libraries just don't do and I will have to look at building it from scratch?
What you could do is simply fill your x-values array with all days up to the current day, beginning from the first day the person weighed himself. (this will support one weight entry per day - if a person weighs himself more often than once a day, you can simply take the e.g. highest value and display it in the chart, and only show the others upon clicking the chart entry)
ArrayList<String> xvals = new ArrayList<String>();
for(int i = startingday; i < currentday; i+= oneday) {
xvals.add(daystring);
}
Each entry in this x-values array will represent one day, in indices from 0 to the last day.
If you want to add the weight measurement for the first day, create a new Entry with x-index 0 and the weight value. If you want to add the weight measurement for the 10th day, add a new Entry with x-index 10 and the weight value.