You are right with the axes in the second example, but you need to specify a dimension with which you can split your series in the first parameter of the addSeries method. Dimple will draw a bubble for each unique value in the specified field, so to draw bubbles in the first example, you can pass your size x.
If you had a price for X and a price for Y, it would look like this:
chart.addMeasureAxis("x", "Price");
chart.addMeasureAxis("y", "Cost");
chart.addSeries("Price", dimple.plot.bubble);
chart.draw();
You will get a bubble for each individual x value. If there are cases when you have 2 Y values for one X value, and you do not want to sum them up, you can transfer both dimensions to a series:
chart.addMeasureAxis("x", "Price");
chart.addMeasureAxis("y", "Cost");
chart.addSeries(["Price", "Cost"], dimple.plot.bubble);
chart.draw();
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