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--- labs:gnuplot [2011/05/01 21:40] – created admin
+++ labs:gnuplot [2011/05/01 21:49] (current) – [Data Files] admin
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 ====== Gnuplot ======
+===== Data Files =====
+A typical Gnuplot data file consists of lines of text, where each line has two numbers, representing an x-value and a y-value. Here is a Gnuplot data file called "bars.dat", followed by an explanation of its contents:
+  # number of days in each month of 2010
+31
+28
+31
+30
+31
+30
+31
+31
+30
+31
+30
+31
+**Explanation:**
+The first line, the one starting with #, is a comment.
+Gnuplot will plot bars of size "y-value" at the corresponding "x-value". For example, gnuplot will draw bars of size 31 at x-value 1, 3, 5, etc.
+===== Plot Files =====
+To plot the "bars.dat" data file, you use a file that contains Gnuplot commands. Here is an example file "bars.plot" that takes "bars.dat" as input and produces an output file "bars.png". The graphic has an xrange of 0 to 13 so that all 12 months will appear and a yrange of 0 to 32. The "plot" command says to use "bars.dat" as the input file and plot the first column (1) as the x-value and the second column (2) as the y-value. The actual image produced appears after the listing of bars.plot:
+  set terminal png large
+  # Modify to change the output file
+  set output "bars.png"
+  set data style boxes
+  set boxwidth 0.4
+  set xtics nomirror
+  set border 11
+  # Modify this code to set the x-range
+  set xrange [0:13]
+  # Modify this line to set the y-range
+  set yrange [0:32]
+  set xlabel "Months"
+  set ylabel "Days in Month"
+  set xtics ("Jan" 1, "Feb" 2, "Mar" 3, "Apr" 4, "May" 5, "June" 6,\
+  "July" 7, "Aug" 8, "Sep" 9, "Oct" 10, "Nov" 11, "Dec" 12)
+  set key below
+  plot 'bars.dat' using 1:2 fs solid title "Num Days"
+===== Executing Gnuplot =====
+To execute Gnuplot, in the terminal run gnuplot <plotfile>
+For the above example, you would execute
+  gnuplot bars.plot
+There should be no output (gnuplot is a bad parent), but you should now see the output file in the directory if you run ls.
+To create your own graph file, you will probably need to modify
+  *  the output file's name
+  *  the input file's name
+  *  the x-axis
+  *  y-axis range and labels
+  *  the xtics (x-axis labels).