pl

A simple plot command based on gnuplot.

What can pl do for you?

Gnuplot is a very powerfull language to make plots. However, it is very complex and, consecuently, it is difficult to make good plots without previous experience. pl tries to solve this issue providing a simple command to make plots in just a line of code.

pl supports 2D plots and generates images in png, such as the following one:

You only has to pass the file with the data as an argument and pl will do the plot for you! For example, the previous image was plotted using pl example.csv -t "An example with pl" -x "X Axis" -y "Y Axis".

The command pl -e provides the file example.csv.

Instalation

1. You can clone the repository with git clone or download the zip file.
2. The code needs to be compiled using make, which will ask you to install the dependencies that you don't have already installed.
3. If you want to use pl as an usual bash command, you should add the bin directory to the global variable PATH. To accomplish this, add the following line of code to your .bashrc file:

PATH=$PATH:<absolute path to /pl/bin/>

Examples and parameters

pl uses LEX to detect each parameter in lineal time. Consecuently, the parameters can be given in any order and the program will receive the formats that he is expecting to. Thus, the two following lines of code are equivalents:

pl example.csv -t "An example with pl" -x "X Axis" -y "Y Axis"
pl -y "Y Axis" example.csv -x "X Axis" -t "An example with pl"

Files with data

pl can plot multiple files at the same file. The files passed to pl must contain at least two columns separated by a delimiter. The first column contains the abscissas of the points to plot. Each of the other columns must contain an ordinate for each abscissa, defining a point which will be plotted by pl. The points in the same column represent a function and are plotted with the same color. For example, the following one is a file with 4 lines:

0,0,1,2,3
1,0,1,2,3
2,0,1,2,3
3,0,1,2,3

If it is plotted using pl lines1.csv, then we obtain the following image:

The previous file follows the csv standard. However, you could use a different delimiter than a comma with the parameter -d <character>.

These kinds of graphics are very useful comparing algorithms' performance. However, algorithms' data could be in various files with different abscissas' values. pl accepts multiple files as arguments, plotting all the data in one image. Let's consider another file with lines:

0,0.5,1.5,2.5,3.5
0.5,0.5,1.5,2.5,3.5
2.5,0.5,1.5,2.5,3.5
3,0.5,1.5,2.5,3.5

Then, we can plot both files at the same time (pl lines1.csv lines2.csv):

Note that we could have used regular expressions in bash to simplify the input: pl *.csv.

If your file name does not contains a dot, then you must pass it using the parameter -f filename.

Simple configurations

The following parameters allows to change the image's name, title, labels and legends.

• -o \<image name> Sets the name of the plotted image.

• -t \<title> Sets the image's title. You can provide a word or a text line between " ".

• -x \<x label> Sets the image's label for the x axis. You can provide a word or a text line between " ".

• -y \<y label> Sets the image's label for the y axis. You can provide a word or a text line between " ".

• -l The program will take the first entry in each column as the legend. If there is no label for the x axis, then the first entry in the abscissas' column will be used instead.

For example, you can use pl lines_legend.csv -o my_plot.png -l -t "Some lines with legend." -y "Y Axis" to plot:

X Axis,Line 1, Line 2, Line 3, Line 4
0,0,1,2,3
1,0,1,2,3
2,0,1,2,3
3,0,1,2,3

Lines' style

By default, pl plots the data using lines and points at the same time. However, you can use another style if you want typing the parameter -s \<style>. It supports 3 different styles: lines, points and linespoints. You could use -sp, -sl and -slp respectively.

In any case, the points and lines' width can be changed using the parameter -w \<line width>, which sets the width to the chosen integer, starting at 0. The width is set to 2 by default.

Colors used in the images

To select the colors, pl uses the HSV space. In this space the colors are represented by 3 components:

• Hue : The attribute of a visual sensation according to which an area appears to be similar to one of the perceived colors: red, green, and blue, or to a combination of two of them.

• Saturation : The intensity of a color relative to its own brightness.

• Value or brightness : The attribute of a visual sensation according to which an area appears to emit more or less light.

By default, pl chooses colors with the same saturation and value. The hue is selected uniformly in the interval in order to obtain different colors. However, if you want to use colors with similar hue, then pl provides the following parameters:

• -c \<color name> : Plots the image with variations of the color chosen. You can choose among: blue, cyan, green, magenta, red and yellow.

• -c \<R,G,B> : Plots the image with variations of the color chosen. You must provide a tuple R,G,B with the color's RGB representation. Each value is an integer between 0 and 255.

The first one converts the chosen color to RGB to perform the computations. The colors generated have similar hue. The brightness is selected uniformly, obtaining dark and clear colors. The colors also have different saturations in order to generate colors as different as possible.

For example, the following image is the result of plotting the file example.png with cyan.

To obtain information about the parameters from the command line you can use pl -h.

Author

Andrés Herrera Poyatos

License

The MIT License (MIT) Copyright (c) 2015 Andrés Herrera Poyatos