The following code shows the format for an Irregular Grid layout that has 10 by 5 points:
! Irregular grid has 10 by 5 points
! Holes have a value of 100.0
! Ten X values are given, and then five Y values
IRGRID 10 5
100.0
20 21.1 23.4 24.4 25.0 27.8 29.9 31.0 32.6 33.2
50.3 51.3 52.6 54.8 59.6
! 50 data points follow
23.34563 12.89239 11.99423 15.781212 18.81988
. . .
Line 4 indicates that the file is in the Irregular Grid format, and has 10 by 5 points. Line 5 shows the hole value (100.0). Line 6 contains the 10 X values, and line 7 contains the 5 Y values.