Making an impulse plot

Impulse or stick plots are another way to represent discrete points. If the line thickness is made large, the impulse plot can be made to look like a bar chart.

How to do it…

The following script illustrates the use of the impulses style:

set samples 30
plot [0:2*pi] sin(x) with impulses lw 2

How it works…

The first command set the number of points used to sample or plot the function. The plot command tells gnuplot to use the impulse style, which draws a line from the x-axis to each y value; the thickness of the line is given by lw 2.

There's more…

A "stem plot" is sometimes used in electrical engineering. It is similar to the impulse plot, but with a mark at the end of each stick; this allows the eye to more easily follow the trend of the data; conversely, the sticks make it easier to read the graph, especially when the data is sparse, compared with a simple point plot. Use the following recipe to create a stem plot of a decaying sine wave, illustrated in the following figure:

set samples 50
plot [0:4*pi] exp(-x/4.)*sin(x) with impulses lw 2 notitle,\exp(-x/4.)*sin(x) with points pt 7

As you can see, we have plotted the same function twice. The first time through plot the impulses, as in the previous script, and the second time we plot the function again with points to draw the dots.

The previous plot shows a typical exponentially damped sine wave; it represents, for example, the motion of a pendulum with friction.