My plotted lines aren't appearing on my output figures - matlab

Question

so I'm processing a bunch of images at the one time, trying to display them all as figures with a series of plotted lines on each individual image as a result of the process. With some help I fixed the figure title issue, However the plotted lines are not appearing on my final figures, below is the code:
inputFolder = fullfile(pwd, 'BMPData');
filePattern = fullfile(inputFolder, '*.bmp');
%Get list of all Bmp Files in Folder
BmpFiles = dir(filePattern)
for i=1:length(BmpFiles)
fname = BmpFiles(i).name;
fullFileNameInput = fullfile(inputFolder,fname);
A = imread(fullFileNameInput);
%// Change
AR=A(:,:,1);
[rows, columns] = size(AR);
y1 = 200;
y2 = 315;
row1 = AR(y1, :); % Extract this line of gray levels from the image.
row2 = AR(y2, :);
figure('name',fname),imshow(A), hold on;
plot([0, columns], [y1, y1], '.b');
plot([0, columns], [y2, y2], '.m');
end
The reason I am doing this is because I want to mark 2 rows (200 and 315) on all my images and then do some statistical analysis on all the pixels in them rows for further processing techniques.

Answer 1

The reason why you're getting columns undefined is due to variable scope. When you define columns in SegmentationNew, columns is only available within the lifetime of SegmentationNew and only visible within SegmentationNew. Once SegmentationNew completes, column is no longer defined.
I honestly can't make heads or tails of what SegmentationNew is doing, but from the looks of it, there is no good reason why you should call it. All you need from it is y1 and y2, which are defined as constants. columns you can determine from the columns of the image. I'm also going to borrow from the duplicate post that Martin J.H. has linked to make naming the figure window more elegant.
To add to this post, your original code was plotting just the points. If you want to plot the lines as well, you need to remove the . characters from your plotting string for each call to plot. Specifically, change .b and .m to b and m respectively.
As such, do this:
for i=1:length(BmpFiles)
fname = BmpFiles(i).name;
fullFileNameInput = fullfile(inputFolder,fname);
A = imread(fullFileNameInput);
%// Change
columns = size(A,2);
y1 = 200;
y2 = 315;
figure('name',fname); %// Change
imshow(A); hold on;
plot([0, columns], [y1, y1], 'b'); hold on; %// Change
plot([0, columns], [y2, y2], 'm');
end