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naninterp

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naninterp

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05 Aug 2005 (Updated )

One dimensional Interpolation over NaNs.

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Description

One-line logically-indexed call to matlab function "interp1"

Fill nan-holes, fast and easy.

>> x = [1 2 NaN NaN 5 6];
>> naninterp(x)

ans =

     1 2 3 4 5 6

Cubic interpolation by default, you should know how to change that :-)

--------------------------------------------------------------------------
function X = naninterp(X)
% Interpolate over NaNs
X(isnan(X)) = interp1(find(~isnan(X)), X(~isnan(X)), find(isnan(X)), 'cubic');
return
--------------------------------------------------------------------------

Acknowledgements

This file inspired Repnan and Interp1gap.

MATLAB release MATLAB 6.5 (R13)
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Comments and Ratings (13)
22 Oct 2014 Chad Greene

This function works as advertised, but lacks sufficient documentation. The function may also benefit from some simple input checks and functionality could be extended with an optional input of interpolation method.

Ashley, a well-documented function which fills NaNs in 2D can be found here: http://www.mathworks.com/matlabcentral/fileexchange/4551

31 Jul 2013 Gwenolé LE PACHE  
20 Jan 2013 Shmuel  
22 Jun 2012 Ashley

Does anyone know how to do this for a 2D matrix?

13 Apr 2012 Joel

Worked great for me!!!

21 Feb 2010 Tina Hegarty

Thank you so much. I've spent so long trying to find a way to do exactly this! Great. :)

27 Feb 2009 David D

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

clear
clc

% Test
Matrice= [ 99 2 3 0 6;
4 5 99 0 0;
7 0 8 99 NaN]
% Matrice bidon pour voir position index
B=[1:1:15];
Z=reshape (B, 3, 5)
% Fin test

% Détection des cas recherchés
Where_NaN= isnan(Matrice);
idx_NaN= find (Where_NaN==1);
idx_0_99= find (Matrice==0 | Matrice== 99);

% Création d'une liste unique d'index des cas recherchés
% Noter que je fais la transposée de idx_0_99 car c'est une colonne de vals
% donc pour la concatenation je dois la mettre en ligne pour aller avec idx_NaN
Lst_NaN_0_99 = [idx_NaN idx_0_99.']

% Remplacement des valeurs par moyenne des valeurs qui entoure position.
% 2 cas particuliers: premières et dernières positions dans les colonnes.
% Les if sont là pour les détecter. Si 1ere position dans colonne, nouvelle
% valeur égale à valeur suivante. Si dernière position, valeur égale à
% valeur précédente.

% Détection format matrice
[lignes, colonnes]= size (Matrice);

% Cas classique (calcul moyenne)
idx_PosiIn= find (rem(Lst_NaN_0_99(:),lignes)~=0 & rem(Lst_NaN_0_99(:),lignes)~=1);
% Calculer si pas de cas non voulus côte à côte
if (Matrice (idx_PosiIn - 1)~= idx_PosiIn(:) & Matrice (idx_PosiIn + 1)~= idx_PosiIn(:))
Matrice (idx_PosiIn)= (Matrice (idx_PosiIn - 1) + Matrice (idx_PosiIn + 1))/2;
end

% Position en haut de colonne
idx_PosiUn= find (rem(Lst_NaN_0_99(:),lignes)==1);
% Calculer si pas de cas non voulus côte à côte
if Matrice (idx_PosiUn + 1)~= idx_PosiUn(:)
Matrice (idx_PosiUn)= Matrice (idx_PosiUn + 1);
end

% Position en bas de colonne
idx_PosiLast= find (rem(Lst_NaN_0_99(:),lignes)==0);
% Calculer si pas de cas non voulus côte à côte
if Matrice (idx_PosiLast - 1)~= idx_PosiLast(:)
Matrice (idx_PosiLast)= Matrice (idx_PosiLast - 1);
end
it's not working can, someone help me

20 Jan 2009 Deepak Trivedi

Thanks! We need a N-D version of this too.

13 Oct 2008 Girts Murans  
30 Jun 2008 Carlos Adrian Vargas Aguilera

Je je, nice little function, which I rader use as a script, but anyway. You should explain in the help that data should be a time series (i.e. equally spaced), you can use 'extrap' to interpolate edges, and use isnan only one time, and set the method as an optional function, use griddatan for N-dimensional array in order to make your function more interesting and is a nice test:

method = 'cubic';
extrap = {'extrap'};
T = reshape(1:length(X),size(X));
inan = isnan(X);
X(inan) = interp1(T(~inan),X(~inan),T(inan),method,extrap{:});

Anyway, good luck

26 Jun 2008 Yasmin M

I love you!!!

29 Nov 2005 moose o'donnell

Thanks a bunch... much simpler than what I was trying to write...

it took me a while to find this, so I'm including the search terms I was using: gap, fill, gapfill,

06 Oct 2005 ho ge

Good job!

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