Q1=2e-9; 
Q2=-2e-9;	
e0=8.854e-12;
r1=[1, 1, 1]*1e-3;
r2=[-2,-1,3]*1e-3;

X=[-3:0.5:3]*1e-3; 
Y=zeros(size(X));  
Z=Y;  
P=[X' Y' Z'];
P(1,:)  		% tako zapišemo prvi vektor

ans =
   -0.0030         0         0  

for i=1:size(X)  

RP(i,:)=P(i,:)-r1  

 end  

RP =
   -0.0040   -0.0010   -0.0010  

RP  

RP =
   -0.0040   -0.0010   -0.0010