Repalce zero element by the number before it ?

If I have array called N,

N = [2     0     7     0     9    10     0     0    11     0     0 ];

I want to create new array M that have [2 2 7 7 9 10 10 10 11 11 11]

Here is other example

N=[ 0     1     4     5     6     7     0    10     0     0     0]

the one I would create is

M=[0     1     4     5     6      7     7     10     10    10 10].

I would replace each zero in array N by the number before it except the first zero.

Thank you in advance.

Answer 1

[Image Analyst]

Faraj:

Did you try the super obvious solution: a very simple "for" loop:

N = [2     0     7     0     9    10     0     0    11     0     0 ];
for k = 1 : length(N)
	if N(k) == 0
		N(k) = N(k-1);
	end
end

Presumably so. Were you looking for some more compact vectorized or function-based solution instead?

Answer 2

[KSSV]

N=[ 0     1     4     5     6     7     0    10     0     0     0] ;
M = N ;
idx = find(N==0) ;     % get the indices of zeros
while ~isempty(idx)    
    idx(idx==1) = [] ;  % remove the index if zero is at one     
    M(idx) = M(idx-1) ; % replace zeros with previous values 
    idx = find(M==0) ;
    idx(idx==1) = [] ;
end

[Willim]

This works but for my entire code , my code keeps running until I pause the run and quit debugging. then type M in my command window then I got the right M.

could you please the algorithm code ?

[KSSV]

Give the value of N. Image Analyist solution is good....go ahead with that.

Answer 3

[madhan ravi]

EDITED

N = [2     0     7     0     9    10     0     0    11     0     0 ];
M=N;
M(M==0)=NaN;
M=fillmissing(M,'nearest')

Gives:

M =

     2     2     7     7     9    10    10    10    11    11    11

N=[ 0     1     4     5     6     7     0    10     0     0     0];
M=N;
M(M==0)=NaN;
M=fillmissing(M,'previous');
M(1)=0

Gives:

M =

     0     1     4     5     6     7     7    10    10    10    10

[Willim]

This does not work because the zero between the 7 and 10 filled by 10 which should be 7

[madhan ravi]

Change 'nearest' to 'previous' , see edited answer.

[madhan ravi]

If you find it helpful you can vote for it.

[Willim]

great it works but the thing is that the frist element could be 1 not 0 all the time

[madhan ravi]

What? Did you see the first example in my answer?