change hour format gnuplot (substract 12 hour)

问题

I have two devices working in paralell, the problem is that one of them was set up 12 hours different than the other (that is, instead of 17:00, marked 05:00). I'm trying to apply this solution: How to read 12h (AM/PM) timeformat in gnuplot

In this way: My data are like this:

#Time   Concentration (#/cm³)   
05:00:14    5902    
05:00:15    5898    
05:00:16    5989    
05:00:17    5921    

And I'm running the folowing code:

set xdata time
set timefmt '%H:%M:%S'
set format x '%H:%M'  
set xlabel "time"

plot  "< awk '{time = $1; if substr(time,1,2) <= 12) add = 12; else add = 0}' data1.txt" u 1:2 t 'CPC1' w l, \
      "data2.txt" u 1:2 t 'CPC2' w l

pause -1

However, the treated data1 file is not being plotted, only the data2 which has the correct timescale. Any idea of solution?

Thanks in advance!

回答1:

You can add the 12 hours directly inside gnuplot. Inside the using statement use timecolumn to get the time in seconds and then add your 12 hours (43200 seconds)

set xdata time
set timefmt '%H:%M:%S'
set format x '%H:%M'  
set xlabel "time"
set style data lines

plot 'data1.txt' using (timecolumn(1) + 43200):2 t 'CPC1',\
     'data2.txt' using 1:2 t 'CPC2'

来源：https://stackoverflow.com/questions/32946517/change-hour-format-gnuplot-substract-12-hour