Histogram with x axis date error

[dmulter]

Maybe I'm missing something easy, but I don't think so. I've been
using gnuplot for many graphs, and have run into a problem I can't
solve for one case. The following data and plot commands graphs
correctly:

Bugzilla_ArrivalsSev.dat:
Date blocker critical major normal total
2008-12-08 1 0 1 0 2
2009-02-13 1 0 0 0 1
2009-02-16 3 1 1 1 6
2009-02-17 1 1 1 1 4
2009-02-18 1 1 1 0 3
2009-02-19 0 0 0 3 3
2009-02-20 1 0 0 1 2
2009-03-03 1 0 1 0 2
2009-06-25 4 3 3 1 11

$ gnuplot
set terminal png nocrop enhanced font Verdana 8 size 400,300
set title "Arrivals By Severity" font "Verdana-Bold,10"
set key outside
set xlabel "Time"
set ylabel "Bug Count"
set xdata time
set timefmt "%Y-%m-%d"
set format x "%m-%d-%y"
set xtic rotate by -75
set style data linespoints
set style fill solid 1.0 border -1
set output "Bugzilla_ArrivalsBySeverity.png"
plot 'Bugzilla_ArrivalsSev.dat' using 1:6 title columnhead

Again, the data file plus the commands above generate a good line
graph with no error. I change the plot commands to a histogram by
modifying 2 lines (set style data histogram, and plot...), I get a
"Need full using spec for x time data" error from gnuplot.

$ gnuplot
set terminal png nocrop enhanced font Verdana 8 size 400,300
set title "Arrivals By Severity" font "Verdana-Bold,10"
set key outside
set xlabel "Time"
set ylabel "Bug Count"
set xdata time
set timefmt "%Y-%m-%d"
set format x "%m-%d-%y"
set xtic rotate by -75
set style data histogram
set style fill solid 1.0 border -1
set output "Bugzilla_ArrivalsBySeverity.png"
plot 'Bugzilla_ArrivalsSev.dat' using 6 title columnhead

I understand the parsing challenge for gnuplot when processing time
data, but I do have the "set timefmt" commands specified, and they
work when doing a line plot as I said before. I have no idea why it
would fail when I use a histogram. Any ideas? Is this a bug?

I'm running 4.2.6 on Mac OS X 10.5.8.

Thanks,
David

[sfeam]

dmulter wrote:

I suspect that the histogram data style doesn't do what you think.
It is intended for comparing parallel columns of data, not for
plotting a single column.

Try instead
set style data boxes
set boxwidth abs <some number>
or
set style data impulses

> I understand the parsing challenge for gnuplot when processing time
> data, but I do have the "set timefmt" commands specified

But histogram plots do not use or want an x-axis coordinate at all.
[There can be exceptions, but your commands don't look like they
are aiming in that direction]

I think you are confusing the program by telling it that the x axis
wants time coordinates, when it is expecting to use the x axis only
to separate 'category 1' from 'category 2', etc. using integers.

[dmulter]

The plot I want to generate is across columns, not in a single column.
What I'm looking for is:

bcmnt bcmnt bcmnt ...
12/8 2/13 2/16 ...

Where "bcmnt" are 5 vertical bars representing the row numeric values
for each row date. So the date runs along the x-axis, and the bars run
represent clustered values for each severity category in the row. Hope
this makes sense.

[dmulter]

My graph output should look like the #2 example from
http://gnuplot.sourceforge.net/demo/histograms.html, but I'm using
real dates instead of just strings on the x-axis.

[dmulter]

> My graph output should look like the #2 example fromhttp://gnuplot.sourceforge.net/demo/histograms.html, but I'm using

> real dates instead of just strings on the x-axis.

One last thing, I simplified the plot command to only use one column
to illustrate the issue. The full command fails with the error on
processing of the first <using> section, but the full version to
generate the plot I want is:

plot 'Bugzilla_ArrivalsSev.dat' u 2:xtic(1) ti col, '' u 3 ti col, ''
u 4 ti col, '' u 5 ti col

[sfeam]

dmulter wrote:

> On Sep 17, 9:07 pm, dmulter <dmul...@gmail.com> wrote:
>> On Sep 17, 9:01 pm, dmulter <dmul...@gmail.com> wrote:

>> > > > $ gnuplot
>> > > > set terminal png nocrop enhanced font Verdana 8 size 400,300
>> > > > set title "Arrivals By Severity" font "Verdana-Bold,10"
>> > > > set key outside
>> > > > set xlabel "Time"
>> > > > set ylabel "Bug Count"
>> > > > set xdata time
>> > > > set timefmt "%Y-%m-%d"
>> > > > set format x "%m-%d-%y"
>> > > > set xtic rotate by -75
>> > > > set style data linespoints
>> > > > set style fill solid 1.0 border -1
>> > > > set output "Bugzilla_ArrivalsBySeverity.png"
>> > > > plot 'Bugzilla_ArrivalsSev.dat' using 1:6 title columnhead

^^^^^^^^^^

>> > > > Again, the data file plus the commands above generate a good
>> > > > line graph with no error. I change the plot commands to a
>> > > > histogram by modifying 2 lines (set style data histogram, and
>> > > > plot...),

>> > > I think you are confusing the program by telling it that the x

>> > > axis wants time coordinates, when it is expecting to use the x
>> > > axis only to separate 'category 1' from 'category 2', etc. using
>> > > integers.
>>
>> > The plot I want to generate is across columns, not in a single
>> > column. What I'm looking for is:
>>
>> > bcmnt bcmnt bcmnt ...
>> > 12/8 2/13 2/16 ...
>>
>> > Where "bcmnt" are 5 vertical bars representing the row numeric
>> > values for each row date. So the date runs along the x-axis, and
>> > the bars run represent clustered values for each severity category
>> > in the row. Hope this makes sense.

Yes, but the point is that the histogram plot style doesn't use
x-coordinates. You can't say: 'plot ... using 1:6 with histograms'
because it only wants a y-coord: 'plot ... using 6 with histograms'.

The program generates sequential integers as the x coordinate internally
so that you get evenly-spaced clusters of histogram bars.
And because it is only generating integral x=0,1,2,3,... it complains
when you tell it that the x-axis is in time units.

>> My graph output should look like the #2 example
>> fromhttp://gnuplot.sourceforge.net/demo/histograms.html, but I'm
>> using real dates instead of just strings on the x-axis.
>
> One last thing, I simplified the plot command to only use one column
> to illustrate the issue. The full command fails with the error on
> processing of the first <using> section, but the full version to
> generate the plot I want is:
>
> plot 'Bugzilla_ArrivalsSev.dat' u 2:xtic(1) ti col, '' u 3 ti col, ''
> u 4 ti col, '' u 5 ti col

That should work to generate evenly spaced clustered labeled with the date,
but you can't use that form of command to change the spacing along x.

The closest I can think of is to use stacked histograms rather than
clustered histograms. Then you can place each stack wherever you
want along the x axis.:

set style data histogram
set style histogram columns

plot newhistogram at <date>, 'day1' using 1, \
newhistogram at <date>, 'day2' using 2, \
...

But it will be hard to pull the x-coordinate date out of the data file,
and I think that to make this work you need to flip your data file
format so that the columns are dates and the rows are the categories.

[dmulter]

Thanks for the explanation, it helps. My real goal was not to change
the spacing along the x-axis, but merely to have gnuplot parse the
date/time data from my data file, and then allow me to reformat for
display in a different format as labels along the x-axis. I didn't
want it to alter the spacing in any way. I can see how the x-axis
commands would be confusing to gnuplot in this case.

Since I can do histograms with x-axis labels, I think there should be
some way to have it parse date/time labels and let me reformat as
needed. It could easily prevent me from using such commands to alter
how it renders the x-axis portion of the graph. FYI, I've just
resorted to formatting the date the way I want in the data file, and
then have it just use it as a label without any x-axis time/date
commands. I do think this is a bug anyway.

[sfeam]

dmulter wrote:
>Bugzilla_ArrivalsSev.dat:
Date blocker critical major normal total
2008-12-08 1 0 1 0 2
2009-02-13 1 0 0 0 1

> Thanks for the explanation, it helps. My real goal was not to change

> the spacing along the x-axis, but merely to have gnuplot parse the
> date/time data from my data file, and then allow me to reformat for
> display in a different format as labels along the x-axis. I didn't
> want it to alter the spacing in any way. I can see how the x-axis
> commands would be confusing to gnuplot in this case.

Now if you had just explained that in the first place,....

# Simple example using pure string processing
# You can define far more complex reformatting commands if you like
# Change date of the form 2008-12-08 to 08-12-2008
reformat(date) = date[9:10].date[5:8].date[1:4]

# Now plot it, generating tick labels by reformatting contents of column 1
plot 'foo' using 2:xtic( reformat(stringcolumn(1) )

> Since I can do histograms with x-axis labels, I think there should be
> some way to have it parse date/time labels and let me reformat as
> needed.

See also the available functions strftime() and strptime()

> It could easily prevent me from using such commands to alter
> how it renders the x-axis portion of the graph. FYI, I've just
> resorted to formatting the date the way I want in the data file, and
> then have it just use it as a label without any x-axis time/date
> commands. I do think this is a bug anyway.

At this point I've lost track of what "this" is, that you think is a bug.