Graph plotting of red pixel vs number of images

I would like to calculate the red pixel count for every image in this folder and then plot a graph of red pixel count vs the number of images. The red pixel count must correspond to the image no. This is my code.

%for loop

clc;

clear;

close all;

fontSize=10;

myFolder='G:\FYP2\Time Frames\Frame 24';

if ~isdir(myFolder)

errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
uiwait(warndlg(errorMessage));
return;

end

filePattern = fullfile(myFolder, '*.png');

theFiles = dir(filePattern);

numberOfImages=length(theFiles);

red_counts = zeros(1, numberOfImages);

redCount=0;

for k=1:numberOfImages

fullFileName = fullfile(myFolder, theFiles(k).name);

thisImage=double(imread(fullFileName));

[rows, columns, numberOfColorBands] = size(thisImage);

redBand=thisImage(:,:,1);

    %THRESHOLD LEVELS

redThresholdLow=215;

redThresholdHigh=255;

redMask=(redBand>=redThresholdLow) & (redBand<=redThresholdHigh);

    %Count pixels

redCount=sum(redMask(:)>0);

red_counts(k)=redCount;

end

plot(red_counts, numberOfImages, '-r*');

set(gca, 'xTickLabel', 1:1:numberOfImages);

ylabel('Red pixel count');

xlabel('Number of images');

[Walter Roberson]

Duplicates http://uk.mathworks.com/matlabcentral/answers/263576-graph-plotting-of-number-of-red-pixels-vs-number-of-images