In this post I will show you how to calculate and plot the Lissajous Curves using C and Gnuplot.

We will use the following information:

We will create a program that calculates the values of the x and y for various values and for different n and store these values in a txt file. Then just plot it using Gnuplot.

We will create two functions called ‘x’ and ‘y’, that contain the definition of x and y respectively.

### PROGRAM:

/************************************ ********LISSAJOUS FIGURES ********** ************************************/ #include<stdio.h> #include<math.h> double x(double theta){ return sin(theta); } double y(double theta, double A,double n, double delta){ return A*sin(n*theta+delta); } main(){ double theta; FILE *fp=NULL; double A,n,delta; fp=fopen("lissajous.txt","w"); /*Loop to calculate and store data-points*/ for(theta=0;theta<=4*M_PI;theta=theta+0.01){ /*Change A, n or delta here*/ A=1; n=3; delta=M_PI/4; fprintf(fp,"%lf\t%lf\n",x(theta),y(theta,A,n,delta)); } }

When you run the above C, it will generate a file called ‘lissajous.txt’ which would contain 2 columns of data-points.

The first column contains the ‘x’ values and the next one is for ‘y’ values.

These can be easily plotted using Gnuplot by using the following commands:

### GnuPlot Command

`plot 'lissajous.txt' w l`

### OUTPUT

For different values of the output looks as follows:

### Resources:

https://academo.org/demos/lissajous-curves/