question about binary plot data

[Chris K <gnu...@li...>]

As I am trying to send data to gnuplot, I have been experimenting to understand
how to pipe data to stdin.


Short version: It is possible to put ascii data after a plot command with more
than one blob (several sections that end with the line "e") Can I send more that
one binary blob?

In particular, I was seeing if I could send binary data via stdin:

cat "command-1.gp" "binary.dat" | gnuplot

where the command-1.gp file is one line:

plot "-" binary record=5x2 using 1:2 with linespoints

and the binary.dat file is 10 floats (40 bytes)

That worked like I expected it to, parsing the binary file as "x1 y1 x2 y3 x3 y3
x4 y4 x5 y5" and plotting markers at (x1,y1) (x2,y2),...

When I tried something more complicated, it failed:

plot "-" binary record=5x2 using 1:2 with linespoints,\
     "-" binary record=5x2 using 1:2 with linespoints

cat "command-2.gp" "binary.dat" "binary.dat" | gnuplot

The error message seems to indicated the second "-" is the problem:

gnuplot> plot "-" binary record=5x2 using 1:($2) with linespoints,     "-"
binary record=5x2 using 1:($2)**2 with linespoints

                                  ^
         line 0: warning: Skipping data file with no valid points

The documentation page explains that:

> General binary data can be entered at the command line via 
the special file name '-'. However, this is intended for use through
a pipe where programs can exchange binary data, not for keyboards.
There is no "end of record" character for binary data.
Gnuplot continues reading from a pipe until it has read the
number of points declared in the array qualifier.

But I used a record qualifier.  And I don't know how to simulate the array using
records (even given that I can resort the order of the binary data).  Both
"array=5,5 index0" and "array=5,5 index 1" work like I expect.  But I don't see
how i can make an (x,y) plot from index 0 and index 1.

Can gnuplot do the same ascii data tricks with binary data?