Gnuplot String Data - Graphics

In article <1183472530.450170.209090@q75g2000hsh.googlegroups.com>,
<heinemann.stefan@gmail.com> wrote:
>I have a datafile with string data in certain columns. I tried to
>display this as described in the documentation on page 23:
>
>plot 'file' using 2:3
>
>(let's assume that in column 2 is the string data)
>
>Now gnuplot tells me this error:
>
>warning: Axis range undefined due to improper data values. NaN? Inf?
> ^
> All points x value undefined
>
>any ideas why this doesn't work?

Yes. That command does not by itself tell gnuplot what you are
trying to plot (lines, points, boxes, labels, ???). The program
makes a guess based on the number of columns. In your case this
is two ('using 2:3') but the best guess for two columns is
"points using x coordinate from column 2 and y coordinate from
column 3". Since column 2 is in reality a string, it doesn't
work as a y coordinate and therefore you get no valid points.

You probably want either:

# columns 1,2,3 contain x coord, y coord, string
plot 'file' using 1:2:3 with labels

or

# implicit x coord, y in column 2, string in column 3
plot 'file' using 0:2:3 with labels
--
Ethan A Merritt

Thanks for your reply.

On Jul 3, 6:31 pm, merr...@u.washington.edu (Ethan Merritt) wrote:
> Yes. That command does not by itself tell gnuplot what you are
> trying to plot (lines, points, boxes, labels, ???). The program
> makes a guess based on the number of columns. In your case this
> is two ('using 2:3') but the best guess for two columns is
> "points using x coordinate from column 2 and y coordinate from
> column 3". Since column 2 is in reality a string, it doesn't
> work as a y coordinate and therefore you get no valid points.

I see. Can I make it work as a coordinate? So on one axis I have
the strings that occure in the second column and on the other axis
I have a numeric value (third column) and then points.

Something in the direction like

plot 'file' using 0:3:xticlabels(2) with points

Now the problem here is that if for example the string 'A' occures
twice in the datafile, there will be two A tics on the axis with one
point each instead of one A tic with two points.

In article <1183531356.144671.235530@k29g2000hsd.googlegroups.com>,
<heinemann.stefan@gmail.com> wrote:
>
>I see. Can I make it work as a coordinate? So on one axis I have
>the strings that occure in the second column and on the other axis
>I have a numeric value (third column) and then points.

Sorry, I don't understand how you want it to look.
Could you draw a sketch somehow?



--
Ethan A Merritt

On Jul 4, 7:48 pm, merr...@u.washington.edu (Ethan Merritt) wrote:
> Sorry, I don't understand how you want it to look.
> Could you draw a sketch somehow?

I want it to look like in that picture:
http://codedump.ch/stefu/tmp/strings-on-axis.png

You might think now, "but it already does look like this". Yes it
does,
but not with the 'using' feature of gnuplot. I use gnuplot within a
python
program, so the program reads the data, maps the strings to the tics
and passes it to gnuplot. After the new release I hoped I could let
gnuplot manage this...

In article <1183531356.144671.235530@k29g2000hsd.googlegroups.com>,
>
>Can I make it work as a coordinate? So on one axis I have
>the strings that occure in the second column and on the other axis
>I have a numeric value (third column) and then points.
>
>plot 'file' using 0:3:xticlabels(2) with points
>
>Now the problem here is that if for example the string 'A' occures
>twice in the datafile, there will be two A tics on the axis with one
>point each instead of one A tic with two points.

How about this. Data file contains

A <y-coord>
D <y-coord>
A <y-coord>
C <y-coord>
....

Predefine a mapping function:

xcoord(char) = char eq "A" ? 1 \
char eq "B" ? 2 \
char eq "C" ? 3 \
char eq "D" ? 4 \
char eq "E" ? 5 \
... and so on ...

Plot command is then

plot <file> using (xcoord(strcol(1)):2 with points

or, to be more similar to the sketch you gave

plot <file> using (xcoord(strcol(2)):2:1 with labels
--
Ethan A Merritt

Did the solution proposed work for someone, I am trying it and I get an error :
gnuplot> xcoord(char)=char eq "A" ? 1
^
';' expected