Question

My data file has four columns because opencv saves elements in an n x 4 form in xml when exporting a cv::Mat to xml.

How can I concatenate these four columns into one?

reset

set terminal postscript eps enhanced
set output 'imp.eps'
set pm3d
set palette model HSV defined ( 0 0 1 1, 1 1 1 1 )
set style data histogram
set colorbox user
set origin 0.0,0.10
set size ratio 0 1,0.8
set colorbox horizontal origin graph 0.0, -0.15, 0 size graph 1, 0.05, 0 noborder 

set xrange [0:4096]
plot 'var_imp_first_run.data' using 1

set output

I have 4094 elements, and this example creates an histogram where the first 1024 is plotted. I need to append column 2 from x=1024:2048. Please ignore the colorbox stuff; I’m just playing around to learn gnuplot.

I found out that following solve my problem above.

set xrange  [0:4096]
plot newhistogram at 0, 'var_imp_first_run.data' every:: 7 using 1,\
  newhistogram at 1024,'var_imp_first_run.data' every:: 7 using 2,\
   newhistogram at 2048,'var_imp_first_run.data' every:: 7 using 3,\
      newhistogram at 3072,'var_imp_first_run.data' every:: 7 using 4;

Then I found out that it was not what I wanted, because the data are arranged as entries,

x1,x2,x3,x4
x5,x6,x7,x8
and so on.

So what I really need is a histogram that plots the rows before columns. Is it possible?

Answer 1

If you want it to read

x1
x2
x3

instead of

x1,x2,x3

Then (assuming you are on *nix) use

plot 'cat var_imp_first_run.data | tr "," "\n" |' using 1

This is calling the following command and reading the output via the pipe at the end:

cat var_imp_first_run.data | tr "," "\n"

Here, tr is just transcribing commas as newlines.