concept tic label in category gnuplot

This is an excerpt from Manning's book Gnuplot in Action. Login to get full access to this book.

Both x and y values are printed to the file as two separate columns. If the plot contains several curves, they’re written to the file one after another, as separate data blocks. The data format for each column is equal to the format used for the tic labels of the corresponding axis (see section 8.3.3). The third column contains a marker indicating whether this data point was within the plot range or outside of it: i for “inside,” o for “outside,” or u if the point is undefined.

⁶Traditionally, formatting of tic labels was accomplished using the set format option. This option is still available, but it’s now redundant and should probably be avoided in favor of the more consistent method described in the text.

Figure 8.6. Tic marks at multiples of π and Greek letters used for the tic labels. See listing 8.10.

8.3.5. Reading tic labels from file

Finally, gnuplot can read the tic labels from the input file using the _ticlabels() family of functions as part of the using directive to the plot command. (The underscore _ is again a placeholder for any of the axis identifiers from table 8.1.)

Let’s look at the data file in listing 8.9. The x values are present both in numeric form (column 1) and as strings. Of course, it would be nice to use the strings for the tic labels. Here’s how to do that:

plot "months" u 1:2:xtic(3) w linesp

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The xtic() function takes as argument the number of a column to be used for the tic labels. Equivalent functions exist for the other coordinate axes; labels for the y axis are specified after labels for the x axis.

This is an excerpt from Manning's book Gnuplot in Action: Understanding Data with Graphs. Login to get full access to this book.

Whenever we want to study how some quantity changes over time, we are dealing with a time series. Time series are incredibly common—from stock charts and opinion polls to fever curves. Unfortunately, they pose special challenges, since the tic labels we would like to use for the x axis (such as the names of months or weekdays) aren’t strictly numeric.

Finally, providing an empty string as format specifier to set format is a way to suppress the generation of tic labels, although the tic marks will be drawn.

Figure 7.3. The graph generated using the commands in listing 7.4. Note the tic marks at multiples of π and the Greek letters used for the tic labels.

Listing 10.3. Showing two plots side by side using multiplot mode—see figure 10.4

lgn( x, s ) = exp(-0.5*(log(x)/s)**2)/(x*s*sqrt(2*pi)) # Log-normal clgn( x, s ) = 0.5*(1+erf(log(x)/(s*sqrt(2)))) # Cumulative set multiplot layout 2,1 set bmargin 0 # Switch OFF bottom margin of the top panel set format x "" # ... and eliminate tic labels for the x-axis set ytics 0.2,0.2 # Suppress the tic label for y=0 (start,step) set key bottom plot [0:2.5][0:1] clgn(x,0.5) t "s=0.5", clgn(x,1) t "s=1.0", clgn(x,5) t "s=5.0" set bmargin # Restore the bottom margin set tmargin 0 # ... but switch of the top one set format x "%g" # Also restore the tic labels for the x-axis set ytics 0,0.2,0.8 # Suppress tic label for y=1 (start,step,stop) set key top plot [0:2.5][0:1] lgn(x,0.5) t "s=0.5", lgn(x,1) t "s=1.0", lgn(x,5) t "s=5.0" unset multiplot

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