Plotting multiple columns with a for loop in gnuplot, key doesn't work <p>I have file with many columns that I'd like to plot as follows:</p> <pre><code>plot for [i=1:30] 'test' using 1:i w lp </code></pre> <p>This gives the plot I want, but when I do <code>set key</code>, then the key I see has all lines labeled as <code>1:i</code>:</p> <p><img src="https://i.stack.imgur.com/O0Znl.png" alt="enter image description here"></p> <p>How can I make this output more meaningful, by actually displayin the value of <code>i</code>?</p>