FILLZERO (v2.1, may 2008)

replaces zeros of an array with preceeding non-zero values

FILLZERO - replaces zeros of an array with preceeding non-zero values

Y = FILLZERO(X), when X is a vector, returns a vector Y in which each zero in X is changed into the last non-zero value of X that preceeds it. In other words, the sequence ".. A 0 .. 0 B .." is converted into the sequence ".. A A .. A B .."

For matrices, FILLZERO(X) operates on the first non-singleton dimension of X. FILLZERO(X,DIM) operates on the dimension DIM.

Examples:
X = [0 1 0 0 4 0 2 3 0 0 0 8 0] ;
Y = fillzero(X)
% --> Y = [0 1 1 1 4 4 2 3 3 3 3 8 8] ;

X = [1 2 3 0 ; 0 0 4 8; 0 5 0 0 ; 2 0 -2 0 ; 0 1 0 0]
fillzero(X) % ... equals fillzero(X, 1)
% -->
% 1 2 3 0
% 1 2 4 8
% 1 5 4 8
% 2 5 -2 8
% 2 1 -2 8

fillzero(X, 2)
% -->
% 1 2 3 3
% 0 0 4 8
% 0 5 5 5
% 2 2 -2 -2
% 0 1 1 1

FILLZERO can handle NaNs, and Infs. Example:
fillzero([1 0 NaN 0 3 0 Inf 0 -Inf 0 6 0])
% -> 1 1 NaN NaN 3 3 Inf Inf -Inf -Inf 6 6

See also FIND, CUMSUM

This function was inspired by a recent post on CSSM.

Version 2.1, may 2008