First, create a round-robin database that will hold our test data.


rrdtool create testdata.rrd --start 1224453000 --step 1800 \
   DS:testdata:GAUGE:28000:0:U RRA:LAST:0.5:1:1800

Then, populate it with numbers:

rrdtool update testdata.rrd 1224453300:1350535
rrdtool update testdata.rrd 1224467700:1350545
rrdtool update testdata.rrd 1224482100:1350554
rrdtool update testdata.rrd 1224496500:1350560
rrdtool update testdata.rrd 1224514800:1350562
rrdtool update testdata.rrd 1224539700:1350562
rrdtool update testdata.rrd 1224557700:1350562
rrdtool update testdata.rrd 1224576000:1350562
rrdtool update testdata.rrd 1224590100:1350562
rrdtool update testdata.rrd 1224604800:1350562
rrdtool update testdata.rrd 1224622500:1350562
rrdtool update testdata.rrd 1224636900:1350562
rrdtool update testdata.rrd 1224651300:1350562
rrdtool update testdata.rrd 1224669300:1350562
rrdtool update testdata.rrd 1224683700:1350562
rrdtool update testdata.rrd 1224698100:1350562
rrdtool update testdata.rrd 1224712500:1350562
rrdtool update testdata.rrd 1224730500:1350562
rrdtool update testdata.rrd 1224744900:1350562

Let's plot it:

rrdtool graph testdata.png -t testdata --start 1224453000 --end 1224757634 \
   DEF:testdata=testdata.rrd:testdata:LAST 'LINE2:testdata#ff0000'

Result (correct):
http://lh4.ggpht.com/patrakov/SQBmKaXKPtI/AAAAAAAAAOc/O8iAIBxWbw4/s800/testdata.png

Indeed, there is not much change. But let's suppose that we are really
interested in the small change that happened over the week. Let's use
the alternative autoscaling option that, according to the manual page,
is designed specifically for such cases:

rrdtool graph testdata-bug.png -t testdata --start 1224453000 --end 1224757634 \
   -A -Y DEF:testdata=testdata.rrd:testdata:LAST 'LINE2:testdata#ff0000'

Result (wrong):
http://lh4.ggpht.com/patrakov/SQBmKohptyI/AAAAAAAAAOk/29p6b-TuuJw/s800/testdata-bug.png

The buggy image says that testdata is about 35000M, while it is
actually at 1.35M. Misleading plot = data loss.

I should have used the -L 10 option. The manual page warns about that,
although it would be really nice if rrdtool marked the chopped-off
strings somehow. Even Excel's "###" is better.

reopen 503196
retitle 503196 rrdgraph: Truncated strings not marked as such.
severity 503196 normal
thanks

Hi,

On Thu, Oct 23, 2008 at 06:55:25PM +0600, Alexander E. Patrakov wrote:
[...]

Agreed. I'm reopening and retitling this bug. Severity set to "normal"
since imho this is a real bug, not a wishlist item.

Cheers,
Sebastian