How can ı add cie 1931 chromaticity diagram in my code

I found x and y values of picture with my code and I want to show the color in cie 1931 chromaticity diagram with respect to x and y values.

if true
  clc;
clear all;
cam=webcam(1);
cam.Resolution = '640x480';
img = snapshot(cam);
figure(1), imshow(img);
regionimg=img(234:246,314:326);
figure(2), imshow(regionimg);
R=img(234:246,314:326,1);
G=img(234:246,314:326,2);
B=img(234:246,314:326,3);
XYZ=rgb2xyz(img);
figure(3), imshow(XYZ);
X=XYZ(234:246,314:326,1);
Y=XYZ(234:246,314:326,2);
Z=XYZ(234:246,314:326,3);
totalX1=sum(X);
totalX=sum(totalX1);
mnX=(totalX/169)
totalY1=sum(Y);
totalY=sum(totalY1);
mnY=(totalY/169)
totalZ1=sum(Z);
totalZ=sum(totalZ1);
mnZ=(totalZ/169)
xCord=mnX/(mnX+mnY+mnZ)
yCord=mnY/(mnX+mnY+mnZ)
plot(xCord,yCord,'+')
clear cam;
end