How to get pixel value inside a circle

% Demo to show how drawcircle can be used to draw a circle on the image, and crop out that circular region to a new image and compute the mean RGB values and area.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
%-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
% rgbImage = imread('peppers.png');
% rgbImage = imread('coloredchips.png');
rgbImage = imread('peacock.jpg');
hFig = figure;
imshow(rgbImage);
hFig.WindowState = 'maximized';
%-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
% Ask user to draw circle.
button = 'Redraw';
while contains(button, 'Redraw', 'IgnoreCase',true)
    uiwait(helpdlg('Draw a circle'));
    % User draws a circle.  It exits as soon as they lift the mouse.
    hCircle = drawcircle('Color', 'r')
    
    % Get the coordinates in the form [xLeft, yTop, width, height].
    xyCenter = hCircle.Center
    radius = hCircle.Radius
    % Get Mask image.
    mask = hCircle.createMask;
    % Delete the ROI object.
    delete(hCircle);
    % and replace it with a circle in the graphical overlay.
    hVC = viscircles(xyCenter, radius, 'Color', 'r', 'LineWidth', 2);
    % Ask user if the circle is acceptable.
    message = sprintf('Is this good?');
    button = questdlg(message, message, 'Accept', 'Redraw', 'Reject and Quit', 'Accept');
    if contains(button, 'Quit','IgnoreCase',true)
        delete(hVC); % Delete the circle from the overlay.
        roiPosition = [];
        break;
    elseif contains(button, 'Redraw','IgnoreCase',true)
        % OPTIONAL If you want to delete the prior one before drawing the next one.
        delete(hVC);
    elseif contains(button, 'Accept','IgnoreCase',true)
        break;
    end
end
% If you want to delete the circle from the overlay, do this:
delete(hVC); % Delete the circle from the overlay.
%-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
% OPTIONAL: Crop out the circle into a new image.
props = regionprops(mask, 'BoundingBox');
croppedImage = imcrop(rgbImage, props.BoundingBox);
% Display original image
subplot(2, 1, 1);
imshow(rgbImage);
axis('on', 'image')
title('Original Image', 'FontSize', fontSize)
% Display circle over original image.
hold on;
hVC = viscircles(xyCenter, radius, 'Color', 'r', 'LineWidth', 2);
% Display cropped image.
subplot(2, 1, 2);
imshow(croppedImage);
axis('on', 'image')
title('Cropped Image', 'FontSize', fontSize)
% Display circle over cropped image.
xyCenterCropped = [size(croppedImage, 2), size(croppedImage, 1)] / 2;
hold on;
hVC = viscircles(xyCenterCropped, radius, 'Color', 'r', 'LineWidth', 2);
%-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
% OPTIONAL: Get the area and the mean RGB values.
[R, G, B] = imsplit(rgbImage);
Rmean=mean(R(mask));
Gmean=mean(G(mask));
Bmean=mean(B(mask));
area = nnz(mask);
% Update title to show the area and RGB values.
caption = sprintf('Cropped Image.  Mean RGB values = [%.2f, %.2f, %.2f].  Area = %d pixels.',...
    Rmean, Gmean, Bmean, area)
title(caption, 'FontSize', fontSize);
% Close down figure.
% close(hFig);