Graph can import point series from text files where the values are delimited by comma, semicolon, space or tabulator. You use File → Import → Point series... and select the file to import. If you do not specify the type of file, Graph will try to guess the delimitor.

The simplest file looks like this, which uses comma as delimitor:

1,1.7
2,4.3
3,9.5
4,16.2

When imported you get a point series with the coordinates: (1,1.7), (2,4.3), (3,9.5), (4,16.2)

A file with more than two columns will be imported as several point series with the same x-coordinates as specified in the first column. Here is an example with semicolon as delimitor:

50;71,8113997;78,23883162;79,17509098;78,58979676;78,62449077;78,2374541;77,7637696
55;71,81941659;78,17869416;79,2155277;78,48195769;78,6005272;78,22113423;77,7874084
60;71,82943769;78,12714777;79,24787707;78,55661551;78,51266076;78,2129743;77,8425656
65;71,82866684;78,08419244;79,20744036;78,54002489;78,56857576;78,22929417;77,8189268
70;71,81448312;78,06701031;79,18317833;78,55661551;78,55260005;78,24561404;77,75589

When imported you get 7 point series which all share the same x-coordinates.

You can name the point series by starting the line before the data with # followed by the names separated by the same separator as the data. This can also be used for creating several point series that do not share the same x-coordinates by separating the point series with a # and optionally a name for the following point series. The following shows an example with space as separator:

#a b
0 0.2 0.5
1 1.4 -1.7
2 2.1 -2.6
3 3.8 -3.3
#d e
4 4.3 -4.1
5 5.8 -5.5
6 6.1 -6.1
7 7.9 -7.6

This will create four point series each with four data points named a, b, c and d. a and b will share the same x-coordinates, and c and d will share the same x-coordinates.

Not only numbers, but any valid expression can be imported. The following shows an example with semicolon:

1;sin(0.1)
2;sin(0.2)
3;1+sin(0.3)
pi;2*sin(pi/2)