Error when plotting a 2-D vector field

Hello Mathworks Community,

I am trying to plot the electric field vector on matlab , but I am encountering problems. I would like to write the x and why components of the vector field described in the picture below.

When I try to write x component of the vector field i encounter the error mentioned below.

Thank you for your help

>> Nx=100; %number of mesh points on x-axis

>> Ny=100; %number of mesh points on y-axis

>> xrng = linspace (-100,100,Nx);

>> yrng= linspace(0,200,Ny); %specifying the ranges for the x and y axes

>> [X_grd, Y_grd] = meshgrid(xrng,yrng); %2-D grid

>> Eps=8.854*10^-12;

>> E_x=2*(X_grd-2)/k((X_grd-2).^2 +(Y_grd-2).^2).^3/2;

Array indices must be positive integers or logical values.