2

I am trying to plot a bash array using gnuplot without dumping the array to a temporary file.

Let's say:

myarray=$(seq 1 5)

I tried the following:


myarray=$(seq 1 5)
gnuplot -p  <<< "plot $myarray"

I got the following error:

         line 0: warning: Cannot find or open file "1"
         line 0: No data in plot


gnuplot> 2
         ^
         line 0: invalid command


gnuplot> 3
         ^
         line 0: invalid command


gnuplot> 4
         ^
         line 0: invalid command


gnuplot> 5''
         ^
         line 0: invalid command

Why it doesn't interpret the array as a data block?

Any help is appreciated.

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2 Answers 2

Reset to default
3

bash array

myarray=$(seq 1 5)

The myarray is not a bash array, it is a normal variable.

The easiest is to put the data to stdin and plot <cat.

seq 5 | gnuplot -p -e 'plot "<cat" w l'

Or with your variable and with using a here-string:

<<<"$myarray" gnuplot -p -e 'plot "<cat" w l'

Or with your variable with redirection with echo or printf:

printf "%s\n" "$myarray" | gnuplot -p -e 'plot "<cat" w l'

And if you want to plot an actual array, just print it on separate lines and then pipe to gnuplot

array=($(seq 5))
printf "%s\n" "${array[@]}" | gnuplot -p -e 'plot "<cat" w l'
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2 Comments

or echo $myarray | tr " " "\n" | gnuplot -p -e 'plot "<cat" w l'
Avoid useless use of cat! Use STDIN instead, see my answer
1

Plot STDIN

gnuplot -p -e 'plot "/dev/stdin"'

Sample:

( seq 5 10; seq 7 12 ) | gnuplot -p -e 'plot "/dev/stdin"'

or 

gnuplot -p -e 'plot "/dev/stdin" with steps'  < <( seq 5 10; seq 7 12 )

More tunned plot

gnuplot -p -e "set terminal wxt 0 enhanced;set grid;
    set label \"Test demo with random values\" at 0.5,0 center;
    set yrange [ \"-1\" : \"80\" ] ; set timefmt \"%s\";
    plot \"/dev/stdin\" using 1:2 title \"RND%30+40\" with impulse;"  < <(

          paste <(
                seq 2300 2400
          ) <(
                for ((i=101;i--;)){ echo $[RANDOM%30+40];}
          )
)

Please note that this is still one line, you could Copy'n paste into any terminal console.

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