Thanks for the response

The data actually are grouped into data series, in that all the data from a single series appear together. Here's a sample:

0 61 D1
1 69 D1
2 77 D1
... ... ...
8 124 D1
2 48 D2
1 49 D2
... ... ...
3 59 D2
0 68 D3
1 76 D3
... ... ...
11 154 D3

I'd like to get all on the same graph. One potential issue is that the xvalues could be repeated.

Is this what you meant?