Gnuplot: How to load and display single numeric value from data file

Question

My data file has this content

# data file for use with gnuplot
# Report 001
# Data as of Tuesday 03-Sep-2013 
total   1976
case1   522 278 146 65  26  7
case         


        

Answer 1

For linux and similar.

If you don't know the row number where your data is located, but you know it is in the n-th column of a row where the value of the m-th column is x, you can define a function

get_data(m,x,n,filename)=system('awk "\$'.m.'==\"'.x.'\"{print \$'.n.'}" '.filename)

and then use it, for example, as

y = get_data(1,"case2",4,"datafile.txt")

using data provided by user424855

print y

should return 15

Answer 2

Lets start with extracting a single cell at (row,col). If it is a single values, you can use the stats command to extract the values. The row and col are specified with every and using, like in a plot command. In your case, to extract the total value, use:

# extract the 'total' cell
stats 'mydata.dat' every ::::0 using 2 nooutput
total = int(STATS_min)

To sum up all values in the second column, use:

stats 'mydata.dat' every ::1 using 2 nooutput
total2 = int(STATS_sum)

And finally, to sum up all values in columns 3:7 in all rows (i.e. the same like the previous command, but without using the saved totals) use:

# sum all values from columns 3:7 from all rows
stats 'mydata.dat' every ::1 using (sum[i=3:7] column(i)) nooutput
total3 = int(STATS_sum)

These commands require gnuplot 4.6 to work.

So, your plotting script could look like the following:

reset
set terminal pngcairo size 1024,768 enhanced
set output "output.png"
set style fill solid 1.00
set style histogram rowstacked
set style data histograms
set xlabel "Case"
set ylabel "Frequency"
set boxwidth 0.8

# extract the 'total' cell
stats 'mydata.dat' every ::::0 using 2 nooutput
total = int(STATS_min)

plot for [i=3:7] 'mydata.dat' every ::1 using i:xtic(1) notitle, \
     '' every ::1 using 0:(s = sum [i=3:7] column(i), s):(sprintf('%d', s)) \
     with labels offset 0,1 title sprintf('total %d', total)

which gives the following output: