Gnuplotting

Create scientific plots using gnuplot

July 8th, 2011 | 1 Comment

The last entry has plotted all its data from data files, even the signal at 700Hz. In this entry we will see how to plot the signal as a function using the special-filenames property of Gnuplot.

CMR

Fig. 1 Visualization of the comodulation masking release using splot and special-filenames (code to produce this figure, gfb_loop.gnu, gfb.dat, noise.dat)

In Fig. 1 the end result is seen. What we have done is to replace the last splot command from the cmr.gnu file with the following code.

set samples 500
# Define the sinusoid signal to be plotted
sig(y) = y>0.1 && y<0.4 ? 0.45*sin(2*pi*100*y)+2 : 2
# The desired range is 0:0.5, but the samples were created for the
# x-axis, which has a range of 0:1400, therefore we calculate an
# factor to do the plot
fact = 1400/0.5
splot '+' u (700):($1/fact):(sig($1/fact)) w l ls 14

We define the function sig(y) which is a 100Hz sinusoid centered at 2 for values of y between 0.1 and 0.4 and constant 2 else. In order to place this two dimensional function in our 3D plot we use the special-filenames property from Gnuplot, in this case the '+' variant. This tells Gnuplot to use the xrange, apply a sampling of it and return it as first column for the plot command. But for our plot we need the y-axis and not the x-axis, because the x values should be constant at 700 and are therefore given by (700) at the splot command. The values of the first column, given by $1 are scaled by fact in order to match the two axis and are then directly used as y values and given to the sig(y) function for the z values.

1 Comment

  1. Jacquelyn says:

    I’m really loving the theme/design of your site. Do you ever run into any internet browser compatibility issues? A couple of my blog readers have complained about my website not working correctly in Explorer but looks great in Firefox. Do you have any recommendations to help fix this issue?

Leave a Reply