how to do eigenvalues decomposition on correlation/covariance matrix.

i have data set that p1,p2,p3 where all the matrix are 5*20(row*column). i calculated the correlation matrix and eigen value and the eigen vectors. i need to do eigen decomposition and plot them on 3d scatter plot, im stuck on their.

p1 = random data; p2 = random data; p3 = random data;

 R1=corrcoef(transpose(p1));
 [V1,D1]=eig(R1);

 R2=corrcoef(transpose(p2));
 [V2,D2]=eig(R2);

 R3=corrcoef(transpose(p3));
 [V3,D3]=eig(R3);

im stuck on here. thank you