if the index of SubplotExample start from 0, the first two charts are going to be combined

[diegolovison]

The following is a reproducer of what I found while creating my own charts

Replace https://github.com/jtablesaw/tablesaw/blob/master/jsplot/src/test/java/tech/tablesaw/examples/SubplotExample.java#L33 with -1
Example:

AtomicInteger order = new AtomicInteger(-1);

Then, the State no and Scale charts are combined

It took me a while to find out the root cause.