Options explained

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#### Data types
dataX and dataY are always standard JS arrays, but the inner arrays that hold the actual data can be either a standard JS array or a typed array(uint8, int32, float32..).

The data in the inner arrays can be any number.

#### Length of arrays
The inner arrays in dataY hold the Y-axis values for each coordinate. Each new inner array will create a new line to plot on the graph.

The inner arrays in dataX hold the X-axis values for each coordinate. dataX doesn't neccessary need to contain the same number of inner arrays as dataY. The X-coordinates can be implicit.

There are three different possibilities for the coordinates to be interpreted.
* dataX.length == 0: Each coordinate gets the implicit X-value of n+1.
Coordinate: { n+1, dataY[i][n] }
* dataX.length == 1: Each inner array in dataY uses the same inner array in dataX.
Coordinate: { dataX[0][n], dataY[i][n] }
* dataX.length == dataY.length: Each inner array in dataY has each own inner array in dataX.
Coordinate: { dataX[i][n], dataY[i][n] }

NOTE: If dataX has length 0 or 1, then we only have one (implicit or explicit) data set for X. Each inner array in dataY has to have the same length.

NOTE: If dataX has length greater than 1, then dataY.length must be equal to dataX.length and dataY[i].length must be equal to dataX[i].length.

#### Why use separate X and Y arrays?
Many other similar systems use matrices or an arrays of objects to describe each coordinate. Graph on the other hand uses separate X and Y arrays. This has several advantages:

* Increased performance. Accessing members is costly in JavaScript so instead of having to do data[i][1] or data[i].y Graph just do dataY[i].
* Implicit X-coordinates. Less data thats needs processing. Use custom value formatter to get the output you want for X.
* One X for each Y. Possible to plot data sets that have different length and distribution. Not possible with format: {x, y1, y2, y3}
* Can use typed arrays. Less CPU overhead, more memory efficient, possible to transfer between web workers and so on.

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