Chart = Error Invalid position

Just started to learn Observable and need help explaining the following error:

chart = Error: invalid position

Notebook: Interactive Slope Chart / Stephan Haycock | Observable

Any explanation or advice would be appreciated.

As noted by the red caret, the error comes from the dodge function here:

  if (!positions.every(isFinite)) throw new Error("invalid position");

Using the debugger, it looks like you are passing an array of undefined values to the dodge function:

[undefined, undefined, undefined, undefined, undefined, undefined]

My guess from the code is that you are calling dodge three times, once for each of the data.columns which is ["Name", "Race1", "Race2"]. But, the values array in your data only has two elements (presumably for Race1 and Race2). So the third time you are passing undefineds, and hence the dodge function is throwing an error.