My solution for over-popilated X labels

[Jon Allport]

I, like many others, have been suffering with too many labels on the X-axis
(especially for date/time based data).

Feel free to comment on the workaround below which suits my needs. The data
are date/time against values and depending on the 'depth' (i.e. number of
hours back) of data I've elected to only pull a selection of the date/time
values into the $data array, turning the rest into spaces.

My criteria are:

1 hour = labels each minute

1-6 hours = labels each 10th minute

6-24 hours = labels each hour

24 hours = labels each 6th hour

So far that has worked for the graph I want to produce, typically 24-72 hours
wide, drilling down to 1 hour sometimes.

while ($myrow = mysql_fetch_array($result)) {
        if ($depth == 1) {
                $DT = $myrow[0];
        }
        else if ($depth >1 && $depth <= 6) {
                if (substr($myrow[0],15,1)=='0') {
                        $DT = $myrow[0];
                }
                else {
                        $DT = ' ';
                }
        }
        else if ($depth > 6 && $depth <=24) {
                if (substr($myrow[0],14,2)=='00') {
                        $DT = $myrow[0];
                }
                else {
                        $DT = ' ';
                }
        }
        else {
                if (is_integer(substr($myrow[0],11,2)/6) && substr($myrow[0],14,2)=='00') {
                        $DT = $myrow[0];
                }
                else {
                        $DT = ' ';
                }
        };
        $data[] = array($DT, $myrow[1], $myrow[2], $myrow[3], $myrow[4], $myrow[5], $myrow[6], $myrow[7], $myrow[8], $myrow[9], $myrow[10], $myrow[11]);
};

DT field is in the form "YYYY/MM/DD hh:mm:ss"

Hope that's of use to someone.

[lbayuk]

Thanks for posting that.

FYI, there is a short script in the PHPlot "contrib" directory called
"prune_labels" which does something like this. However, it is simplistic, and
probably would not work well with date/time labels. Given the maximum number
of labels you want along the X axis (M), it zaps (M-1) out of every M from
your data array.

Depending on how your database records store the timestamps (assuming they are
not pre-formatted into the database as strings), another approach would be to
make those the X values (not labels) in integer form. I think you do that in
MySQL using the UNIX_TIMESTAMP function. Then you can let PHPlot format them
as date/times, and your X tick increment determines the label density.