title: Gnuplot invalid x range while plotting temperature over time
body: <p>I have a datafile <em>cpuTemp.txt</em> in the Format</p>
  
  <pre><code>09:16;314
  09:19;314
  </code></pre>
  
  <p>and want to plot this using this script:</p>
  
  <pre><code>#!/usr/bin/gnuplot
  set datafile sep ';'                 # seperator ;
  set terminal png                     #output format of graph
  set term pngcairo size 300,300       #resolution
  set output "temp.png"                #name of output file
  set title "Temperature over Time"    #title of graph
  set xlabel "time"                    #horizontal axis name
  set ylabel "celsius * 10"            #vertical axis name
  set timefmt "%H:%M"                  #format of time is source file cpuTemp.txt
  set yrange [0:600]                   #vertical axis range (optional line)
  set xdata time                       #x axis is not numbers, but dates/times
  set format x "%H:%M"                 #format of time labels in axis label
  set grid xtics lc rgb "#888888" lw 1 lt 0    #grey grid on background
  set grid ytics lc rgb "#888888" lw 1 lt 0    #grey grid on background
  plot "cpuTemp.txt" u 1:3 title "temperature" w lines lc rgb '#8b1a0e' lt 1 lw 2
  </code></pre>
  
  <p>now when executing i get warnings and this error which i can't figure out:</p>
  
  <pre><code>me@box:~ $ ./tempPlotter.sh 
  "./tempPlotter.sh", line 15: warning: Skipping data file with no valid points
  
  plot "cpuTemp.txt" using 1:3 title "temperature" with lines lc rgb '#8b1a0e' lt 1 lw 2
                                                                                        ^
  "./tempPlotter.sh", line 15: x range is invalid
  </code></pre>
  
  <ul>
  <li>..why are there no valid points in the datafile?</li>
  <li>..why is the x range invalid?</li>
  </ul>
  
  <p>Thanks in advance,
  Gewure</p>