Gnuplot Data Files
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University of Hawaii at Manoa College of Engineering |
Gnuplot uses data files for plotting discrete data. These data files are plain text files which contain numerical data. Comments can be included in file by placing a pound symbol (#) at the beginning of the line. Each line in the data file contains exactly one data point, and the numbers on each line must be separated by blank spaces. These delimit the columns in a data file.
For two-dimensional plots, each data point can have up to 4 columns. Normally, two columns are used to represent (x, y) pairs. If there are 3 columns, the third column represents the delta value for error bars. Similary, when there are 4 columns, the last two columns represent the low value and high value of y, respectively. You can also omit the x column, in which case Gnuplot will assign x values of 0, 1, 2,... for each successive point. Blank lines within the data files will cause the plot to be broken between those points.
For three-dimensional plots, each data point can have up to 3 columns. Normally, three columns are used to represent (x, y, z) triplets. The x and y columns may be omitted, using the first column for the z column, in which case Gnuplot will assign x and y values of 0, 1, 2,... for each successive point. Blank lines within data files in this case separates groups of y-coordinate points. data files. (With only the z component specified.)
The Gnuplot commands plot and splot use data files for data plots. See the sections in this tutorial pertaining to data plots for 2- and 3-dimensional plots.