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Finding the outline of part of a matrix

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Claire
Claire on 17 Apr 2013
I have a 2D matrix of latitude and longitude coordinates that I have used to create a mask. The mask is comprised of NaNs and 1s, depending on if the grid box is included in my mask.
What I want to do is find the coordinates of the boundary of this mask, so that I can plot a line around the shape designated by the 1s.
For example:
NaN NaN NaN NaN NaN
NaN 1 1 NaN 1
NaN 1 1 1 1
NaN NaN NaN 1 NaN
How do I draw a line around the shape seen in the 1s, and save the coordinates of this line so that I can overlay it in other plots?
I've tried using contour, but it gives diagonal lines, where I only want horizontal or vertical lines.
I found this thread http://www.mathworks.com/matlabcentral/newsreader/view_thread/304168 but I wasn't able to follow the solution.
Any help would be greatly appreciated.
  1 Comment
the cyclist
the cyclist on 17 Apr 2013
What, precisely, do you want the output to be, when the input is the matrix you gave us?

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