Array manipulation?

Hi,

I'm looking for a piece of code that will replace NaN values in an array with the value immidiatly on top of the NaN value, I have paste an example below where I have replaced the values one by one, but that can hardly be the best way. would appreciate any assistance.

PPP =

        2002
         NaN
         NaN
        2008
        2010
        2012
         NaN
        2016
        2018
        2020

PP =

        2002
        2002
        2002
        2008
        2010
        2012
        2012
        2016
        2018
        2020

Answer 1

[Walter Roberson]

while true
  K = find(isnan(PP),1,'first');
  if isempty(K); break; end
  PP(K) = PP(K-1);
end

Answer 2

[Teja Muppirala]

This should be simple enough. Obviously the first element can't be a nan though.

PP = PPP;

for n = 1:numel(PP)
   if isnan(PP(n))
       PP(n) = PP(n-1);
   end
end

[Walter Roberson]

Why not start the "for" loop at 2 to prevent the possibility of indexing at 0 ?

[Teja Muppirala]

Yeah, that's a good point. My thinking was that you'd probably want to have an error there if you did in fact accidentally have a nan at the beginning.

Answer 3

[Andrei Bobrov]

fd1 = find(isnan(PPP))
PPP(fd1) = 0;
a = unique([fd1;fd1-1])
p = PPP(a);
PPP(a)=cell2mat(cellfun(@(x)cumsum(x),mat2cell(p,diff(find([p;1])),1),'UniformOutput', false))