How to detect a particular contour in a matlab plot?

I'm trying to extract a particular outline from a matlab pcolor plot (generated from a Matrix named 'M' which is uploaded here as well) as shown in this image. Original Plot

However I would like to extract the contour only, as shown here. (The yellow color line is the one which I would like to extract and is highlighted here for illustration purpose) Required Plot

But I'm getting the result as the following. ( I don't require any other bits/clutter apart from the curve) Obtained Plot

I'm applying the following code on the Matrix M to obtain the in the erroneous result.

 [~, threshold] = edge(M, 'sobel');
 fudgeFactor = 0.6;
 BWs = edge(M,'sobel', threshold * fudgeFactor);
 se90 = strel('line',6,70);
 se0 = strel('line',3,90);
 BWsdil = imdilate(BWs, [se90 se0]);
 BWnobord = imclearborder(BWsdil,18);
 seD = strel('cube',3);
 BWfinal = imerode(BWnobord,seD);
 BWfinal = imerode(BWfinal,seD);
 pcolor(BWfinal);colormap(jet); shading interp;colorbar;

How to obtain only the contour as required? Do I have to use any edge detection filters or do I have to perform smoothing prior to applying any filters? Thanks for any pointers or suggestions to accomplish this.

Answer 1

[Walter Roberson]

If you already know the [x y] path, then you could consider improfile() . Or just call interp2 directly, similar to https://www.mathworks.com/matlabcentral/answers/342101-how-do-you-get-an-arbitrary-1-dimensional-line-scan-from-a-2d-matrix#comment_457886

[Sachin Nag]

I don't know the rows and columns or [x y] values. Is it possible in some way to do it by detecting the edges/contours or something similar?

[Walter Roberson]

It sounds to me as if you need something like envelope detection

https://www.mathworks.com/help/signal/ref/envelope.html and https://www.mathworks.com/help/signal/ug/envelope-extraction-using-the-analytic-signal.html

However as you are working in 2D then perhaps what you should use is boundary() (requires R2014b or later; if you are using an earlier release look in the File Exchange for "active contours"