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replacing NaN with it previous element

Asked by antonet on 8 Aug 2012
Dear all,
I have
K={
'IT' 'ooil' 'TTT' [ 0] [4.1583]
'IT' 'ooil' 'TTT' [ 0] [4.0339]
'IT' 'ooil' 'TTT' [ 0] [3.9389]
'IT' 'ooil' 'TTT' [ 0] [3.9676]
'ITn' 'ooilb' 'TTT' [ 0] [3.9313]
[NaN] [ NaN] [NaN] [ 0] [3.9313]
'IT' 'ooil' 'TTT' [ 0] [3.8720]
'ITcv' 'ooila' 'TTT' [ 0] [3.8829]
[NaN] [ NaN] [NaN] [ 0] [3.9313]
'IT' 'ooil' 'TTT' [ 0] [3.8681]
'ITf' 'ooilg' 'TTT' [ 0] [4.3944]
[NaN] [ NaN] [NaN] [ 0] [3.9313]}
And I want to replace the NaNs in each column with its previous element of the same column
That is,
K={
'IT' 'ooil' 'TTT' [ 0] [4.1583]
'IT' 'ooil' 'TTT' [ 0] [4.0339]
'IT' 'ooil' 'TTT' [ 0] [3.9389]
'IT' 'ooil' 'TTT' [ 0] [3.9676]
'ITn' 'ooilb' 'TTT' [ 0] [3.9313]
'ITn' 'ooilb' 'TTT' [ 0] [3.9313]
'IT' 'ooil' 'TTT' [ 0] [3.8720]
'ITcv' 'ooila' 'TTT' [ 0] [3.8829]
'ITcv' 'ooila' 'TTT' [ 0] [3.9313]
'IT' 'ooil' 'TTT' [ 0] [3.8681]
'ITf' 'ooilg' 'TTT' [ 0] [4.3944]
'ITf' 'ooilg' 'TTT' [ 0] [3.9313]}
Thanks in advance

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3 Answers

Answer by Azzi Abdelmalek
on 8 Aug 2012
 Accepted Answer

res=K,
for k=1:size(K,1);
if isnan(K{k,1});
res(k,1:3)=K(k-1,1:3);
end;
end

  1 Comment

thank you all!

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Answer by Isktaine on 8 Aug 2012
Edited by Isktaine on 8 Aug 2012

Save this function then use it on K:
function K = RemoveNaNs(K)
[rows,cols]=size(K); %Works out how many rows and columns there are
for p=1:rows
for q=1:cols
if isnan(K{p,q})==1 %If there is a NaN entry
K{p,q}=K{p-1,q}; %Replace it with the entry from the previous row.
end
end
end
end
Is this clear?

  3 Comments

What if there are two nans adjacent?
That wouldn't be a problem because you've already replaced the 1st nan. The only problem would be a nan in the very 1st line. Then p-1=0 and you would get an error. So p needs to start at 2 and there needs to be an initialization in case the first row has a nan.
Yeah John is right. I didn't know what antonet would want the value to be if there was a NaN in the first row, so I didn't address this.
Thanks Lucas! :)

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Answer by Thomas
on 8 Aug 2012

K={
'IT' 'ooil' 'TTT' [ 0] [4.1583]
'IT' 'ooil' 'TTT' [ 0] [4.0339]
'IT' 'ooil' 'TTT' [ 0] [3.9389]
'IT' 'ooil' 'TTT' [ 0] [3.9676]
'ITn' 'ooilb' 'TTT' [ 0] [3.9313]
[NaN] [ NaN] [NaN] [ 0] [3.9313]
'IT' 'ooil' 'TTT' [ 0] [3.8720]
'ITcv' 'ooila' 'TTT' [ 0] [3.8829]
[NaN] [ NaN] [NaN] [ 0] [3.9313]
'IT' 'ooil' 'TTT' [ 0] [3.8681]
'ITf' 'ooilg' 'TTT' [ 0] [4.3944]
[NaN] [ NaN] [NaN] [ 0] [3.9313]}
% needs only 3 lines of code
A=K;
[r,c]=find(cellfun(@(V) any(isnan(V(:))), A));
K(r,c)=K(r-1,c)

  2 Comments

That's certainly more brief than my code, could you explain what V is?
Thomas
on 8 Aug 2012
@V creates an anonymous function. The cellfun documentation has more on it.. http://www.mathworks.com/help/techdoc/ref/cellfun.html

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