Number of columns in data file using STATS

Question

Based on the answer to this question, I'd like to determine the amount of columns in my file.

The file looks like this:

Header,,Header2,,Header3,,
1,2,3,4,5,6
11,12,13,14,15,16

When I now try to use the stats command:

stats 'data.dat'
max_col = STATS_columns

Gnuplot gives the error that there's bad data on line 1 of file data.dat which obviously is the header. If I remove the header, everything's fine, but I'm planning on using columnheader for automated labelling (as discussed e.g. here) of the curves, so removing the header is not a solution.

If it matters: I'm working on a Windows-machine.

Answer 1

As hinted in the comments, the solution is simply modifying the command like this:

stats 'data.dat' skip 1
max_col = STATS_columns

Answer 2

Be aware that STATS_columns will not necessarily give you the maximum number of columns in a file or datablock. Apparently, it will just give you the number of columns in the first data row. If following rows have more columns stats will not take this into account.

If you need to know the maximum number of columns of data which is not a regular table, the following code (tested in gnuplot 5.2.5) is counting the separators of all lines in a "irregular" datablock and tells you the maximum. Well, possible drawback: commented lines containing separators will also be included. A file has to be loaded to a datablock first. I am happy to learn if there is a better way.

### maximum number of columns in datablock
reset session

$Data <<EOD
11  12  33
21  22  23  24  25
31  32  33  34  35  36  37  38  39
41  42  43  44  45
51  52
EOD

# Method with stats
stats $Data nooutput
print "STATS_columns: ", STATS_columns

# Method with counting separators
CountChar(s,c) = int(sum[Count_i=1:strlen(s)] (s[Count_i:Count_i] eq c))
ColMax = 0
Separator = "\t"
do for [i=1:|$Data|] {
    ColCount = CountChar($Data[i],Separator)+1
    ColMax = (ColCount > ColMax ? ColCount : ColMax)
}
print "Maximum Columns: ", ColMax
### end of code

Result:

STATS_columns: 3
Maximum Columns: 9