This is best explained by way of an example. Suppose the file data contains the lines:
x y z v - - - - 0 1 2 3 1 3 4 2 3 4 5 3 4 5 6 4 5 6 7where exactly one tab-character separates the columns (note that the second y-value is missing - denoted by two adjacent tabs).
The command math < data yields:
x y z v Type - - - - ---- 5 4 5 5 Freq 10 13 20 25 Sum 2 3 4 5 Mean 1.58114 1.70783 1.58114 1.58114 Stddev 4 5 6 7 Maximum 0 1 2 3 Minimumon the standard output.
The output should be self-explanatory.
Math assumes that two tabs in a row denotes a missing value. This is usually a correct assumption - an empty columns is normally a missing value and should not be counted or used in a sum.
Math only does simple checks for the number of digits appropriate for output. Sometimes this yields messy output, although most cases should be reasonable, as in the above example.
No checks for invalid data are made.