# replace nan in a matrix with specific values

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Hajar Alshaikh on 15 Nov 2022
Commented: Hajar Alshaikh on 15 Nov 2022
I do not know why the following code does not work
I have a matrix F which has some of nan entries, and i have saved the last row of this matrix as N_lastrow. then I want to replace all nan entries in this row such that if F is 4*4 matrix and if N_lastrow(4,4)= nan , then replace it directly by the mean of the whole rest of entries in F. However, any other nan values such that if N_lastrow(1,2)=nan, we have to replace it by the value of of F(3,3) and if it is also nan I will replace it by F(2,4), and if it is also nan then replace it by the mean of the whole rest of entries.
THIS IS THE CODE
f;
N_lastrow=f(n,:);% where n is the number of rows in f
for k=1:n
if isnan(N_lastrow(1,k))
if k==n
N_lastrow(1,k)=nanmean(f,'all')
break
end
for m=n:1
if m-1 >0
N_lastrow(1,k)=f(m-1,k+1)
if ~isnan(f(m-1,k+1))
break
end
else
N_lastrow(1,k)=nanmean(f,'all')
end
end
else
N_lastrow(1,k)=f(n,k)
end
end
N_lastrow

Kevin Holly on 15 Nov 2022
Can you give clarity to what you want? To me, it sounds like you want something like this:
f = [1 2 3 2; 4 5 6 1; 7 8 9 2];
f(4,4) = NaN
f = 4×4
1 2 3 2 4 5 6 1 7 8 9 2 0 0 0 NaN
N_lastrow=f(end,:)
N_lastrow = 1×4
0 0 0 NaN
if isnan(f(4,4))
f(4,4) = f(3,3);
if isnan(f(3,3))
f(4,4) = f(2,4);
if isnan(f(4,4))
f(4,4) = mean(f,'omitnan');
end
end
end
f
f = 4×4
1 2 3 2 4 5 6 1 7 8 9 2 0 0 0 9
N_lastrow=f(end,:)
N_lastrow = 1×4
0 0 0 9
Hajar Alshaikh on 15 Nov 2022
no. if N_lastrow(1,n) is nan then direct f(n,n) = mean(f,'omitnan');
so f(4,4)=f(3,3) is not right
please review the code that I wrote up
my question is why nan still appear after i run my code?

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