Making a matrix of NaN and integers

Question

Janell Lopez 2016-3-1

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回答： Andrei Bobrov 2016-3-2

I'm having trouble with another assignment. We are to design a "mean filter" image processing function, where each pixel of an image is replaced with the average value of its surrounding pixels. One suggested way of doing this was to create a larger matrix where the outer rows and columns are NaN elements, and then for the image's outer rows and columns we can use the NaNMean function.

I have created a row vector of NaN the same size as my image, and a column vector the same size + 2. But I am not sure how to add them to my image matrix--I have tried just the + operator, and concatenation, but I get errors each time. What am I missing?

Thanks!

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Answer 1

Star Strider 2016-3-2

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If I understand correctly what you want to do, this works:

Img = uint8(randi([0 255], 5, 7));                      % Create ‘Image’
[R,C] = size(Img);                                      % Get ‘Image’ Dimensions
nan_border = nan(R+2,C+2);                              % Create NaN Matrix
nan_border(2:R+1, 2:C+1) = Img;                         % Insert ‘Image’ Into NaN Matrix
nan_border =
   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN
   NaN    60    23   185   253   185   201    28   NaN
   NaN   245    65    58    23   142    81    69   NaN
   NaN   158   219   147    82   135   115   134   NaN
   NaN   153   233   207   130   212   192   248   NaN
   NaN    44   179   103    15   219    28   181   NaN
   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN