Gnuplot plotting data from a file up to some row

Question

I have data in some text file which has let\'s say 10000 rows and 2 columns. I know that I can plot it easily by plot \"filename.txt\" using 1:2 with lines . Wh

Answer 1

You can probably cut out the reliance on an external utility (If your system doesn't have them installed for example) using the pseudo-column 0.

see help plot datafile using pseudocolumn

Try something like:

LINEMIN=1000
LINEMAX=2000

#create a function that accepts linenumber as first arg
#an returns second arg if linenumber in the given range.
InRange(x,y)=((x>=LINEMIN) ? ((x<=LINEMAX) ? y:1/0) : 1/0)

plot "filename.txt" using (InRange($0,$1)):2 with lines

(tested on Gnuplot 4.4.2, Linux)

Answer 2

Simpler:

plot "<(sed -n '1000,2000p' filename.txt)" using 1:2 with lines

Answer 3

It appears that the "every" command in gnuplot is what you're looking for:

plot "filename.txt" every ::1000::2000 using 1:2 with lines

Alternatively, pre-process your file to select the rows in which you are interested. For example, using awk:

awk "NR>=1000 && NR<=2000" filename.txt > processed.txt

Then use the resulting "processed.txt" in your existing gnuplot command/script.

Answer 4

I would recommend some commandline tools like sed, grep or bash. In your example

head -n 2000 ./file.data > temp.data

and

tail -n 1000 temp.data > temp2.data

might work. But haven't tested if such large numbers work with head and tail.

Answer 5

Gnuplot ignores NaN values. This works for me for a specified range of the x coordinate. Not sure how to specify row range though.

cutoff(c1,c2,xmin,xmax) = (c1>=xmin)*(c1<=xmax) ? c2 : NaN
plot "data.txt" u 1:(cutoff(($1),($2),1000,2000))