gnuplot-info

[Gnuplot-info] Trouble with Autoscale

[Eric S. <eri...@co...>]

Hi,

 

I have been working with GNU plot and the autoscale function and have been
having some trouble. Using "set autoscale ymax" does not seem to yield the
result that I thought it would. Hopefully someone can shed some light on
this for me. 

Here is an output of my plot directives:

 

 

set data style lines

set grid

set term pbm color

set autoscale ymax

set xrange [0:7]

set tics in

set format x ''

set title "01/04/06 through 01/11/06"

set ylabel "Load Average"

set label 1 "Wednesday 04" at 0.5,-.08 center

set label 2 "Thursday 05" at 1.5,-.08 center

set label 3 "Friday 06" at 2.5,-.08 center

set label 4 "Saturday 07" at 3.5,-.08 center

set label 5 "Sunday 08" at 4.5,-.08 center

set label 6 "Monday 09" at 5.5,-.08 center

set label 7 "Tuesday 10" at 6.5,-.08 center

set xtics ("" 1, "" 2, "" 3, "" 4, "" 5, "" 6, "" 7, "" 8, "" 9, "" 10, ""
11, "" 12, "" 13, "" 14, "" 15, "" 16, "" 17, "" 18, "" 19, "" 20, "" 21, ""
22, "" 23, "" 24, "" 25, "" 26, "" 27, "" 28, "" 29, "" 30, "" 31, "" 32, ""
33, "" 34, "" 35, "" 36, "" 37, "" 38, "" 39, "" 40, "" 41, "" 42, "" 43, ""
44, "" 45, "" 46, "" 47, "" 48, "" 49, "" 50, "" 51, "" 52, "" 53, "" 54, ""
55, "" 56, "" 57, "" 58, "" 59, "" 60)

plot '< cat /data | awk "{ if (\$2 > 004) print \$2 - 004, \$6 }"' title
"host"

 

The labels for the x axis (1-7) do not show up, because the resulting graph
(see http://spot.colorado.edu/~schoelle/untitled.bmp) has it's y values
starting at 2 instead of 0.

I figured with "set autoscale ymax" GNUplot would only adjust the maximum
value on the y axis and leave the minimum values starting at 0. 

I thought maybe I was thinking of this backwards and tried "set autoscale
ymin" - but no change resulted in the graph.

 

What the heck am I doing wrong???

 

Thanks.

 

PS. Please reply to me if you can, I don't know if I can subscribe to the
list/newsgroup.

 

Eric Schoeller

ITS Enterprise Services

University of Colorado at Boulder

 

 

Re: [Gnuplot-info] Trouble with Autoscale

[Hans-Bernhard B. <br...@ph...>]

Eric Schoeller wrote:
> I have been working with GNU plot and the autoscale function and have been
> having some trouble. Using "set autoscale ymax" does not seem to yield the
> result that I thought it would. 

That's because you misunderstood the relation between 'set yrange' and 
'set autoscale'.  In particular, 'set autoscale ymax' will not make any 
difference at all if you never 'set yrange' to some particular value 
before.  The effect you want is most directly obtained by

	set yrange [0:*]

The start-up default for both axes in gnuplot is 'autoscale' with a 
fall-back of [-10:10] for the x range in case you plot only an explicit 
function, without giving any x range.  'set autoscale ymax' in that 
situation has no effect, because the upper end of the yrange is already 
set to be autoscaled.

> The labels for the x axis (1-7) do not show up, because the resulting graph
> (see http://spot.colorado.edu/~schoelle/untitled.bmp) has it's y values
> starting at 2 instead of 0.

The problem with your script is that you never mentioned, anywhere, that 
the y axis was supposed to start at 0.

Re: [Gnuplot-info] Trouble with Autoscale

[Eric S. <eri...@co...>]

Hans-Bernhard Broeker wrote:
> Eric Schoeller wrote:
>> I have been working with GNU plot and the autoscale function and have 
>> been
>> having some trouble. Using "set autoscale ymax" does not seem to 
>> yield the
>> result that I thought it would. 
>
> That's because you misunderstood the relation between 'set yrange' and 
> 'set autoscale'.  In particular, 'set autoscale ymax' will not make 
> any difference at all if you never 'set yrange' to some particular 
> value before.  The effect you want is most directly obtained by
>
>     set yrange [0:*]
>
> The start-up default for both axes in gnuplot is 'autoscale' with a 
> fall-back of [-10:10] for the x range in case you plot only an 
> explicit function, without giving any x range.  'set autoscale ymax' 
> in that situation has no effect, because the upper end of the yrange 
> is already set to be autoscaled.
>
>> The labels for the x axis (1-7) do not show up, because the resulting 
>> graph
>> (see http://spot.colorado.edu/~schoelle/untitled.bmp) has it's y values
>> starting at 2 instead of 0.
>
> The problem with your script is that you never mentioned, anywhere, 
> that the y axis was supposed to start at 0.
Thanks, that helped me out a bunch. I absolutely misunderstood those 
directives. At least now I can get y=0 to show up consistently!

The data I'm plotting can range from y=3 to as great as y=2000 so this 
is causing a lot of problems with the labels along the x axis as I have 
no way of scaling their position correctly in relation to whatever ymax 
is generated by autoscale. So sometimes the labels show up, sometimes 
they are too high (st rattling the y=0 line) and sometimes they are cut 
off along the bottom.
I'm setting the labels like this: set label 1 "Wednesday 11" at 0.5,-.08 
center
the -.08 is obviously the problem, but if i never know what ymax is it's 
tough to compute what that value should be for a particular graph.

Are there any other gnuplot directives that i could issue to 
automatically place the labels at the right y offset?

Thanks for all your help.
Eric

Re: [Gnuplot-info] Trouble with Autoscale

[Hans-Bernhard B. <br...@ph...>]

Eric Schoeller wrote:

> The data I'm plotting can range from y=3 to as great as y=2000 so this 
> is causing a lot of problems with the labels along the x axis 

That's because your way of generating those labels is rather 
sub-optimal.  First of all, placing them via 'set xtics' would almost 
certainly be a better idea than doing that via 'set label'.  Second, if 
you must use 'set label', you should use graph or screen coordinates, 
not data coordinates, in cases where you don't know the data scale.
See 'help label' and 'help coordinate' for more details.