How to replace non consecutive value on a vector?

Hi, I want to replace non consecutive value on a vector, for example:

A=[5,5,5,5,5,4,5,5,5,5,4,4,5,5,5,5,4,4,4,5,5,5,5];

From A, I want to replace the value 4 to 5, provided that 4 comes only once or twice.

So, I want to replace the below 4 (bold) to 5.

A=[5,5,5,5,5,4,5,5,5,5,4,4,5,5,5,5,4,4,4,5,5,5,5];

The result would be..

A=[5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,4,4,4,5,5,5,5];

How can find those 4s and replace them to the value I want?

I want to generalize the code to apply for another cases (not only for this 4 and 5 case)

Many thanks!

Answer 1

[Image Analyst]

You can use bwareafilt if you have the Image Processing Library:

A   = [5,5,5,5,5,4,5,5,5,5,4,4,5,5,5,5,4,4,4,5,5,5,5];
% Get the mode value
modeValue = mode(A)
% Find out where the array is not the mode value
mask = A ~= modeValue
% Extract only those locations where the non-mode values
% are a sequence of 1 or 2 long.
mask = bwareafilt(mask, [1, 2])
% Replace those locations with the mode value
A(mask) = modeValue

modeValue =

5

mask =

1×23 logical array

0 0 0 0 0 1 0 0 0 0 1 1 0 0 0 0 1 1 1 0 0 0 0

mask =

1×23 logical array

0 0 0 0 0 1 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0

A =

Columns 1 through 20

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 4 4 4 5

Columns 21 through 23

5 5 5

See? Only the lengths of 4 that were 1 and 2 long were replaced by 5.

Answer 2

[Davide Masiello]

You could write a function that scans your array in search of the pattern you specify and replaces it with another.

clear
clc

A   = [5,5,5,5,5,4,5,5,5,5,4,4,5,5,5,5,4,4,4,5,5,5,5];
pat = [5,4,5];
rep = [5,5,5];

A = replacePattern(A,pat,rep)

A = 1×23

5 5 5 5 5 5 5 5 5 5 4 4 5 5 5 5 4 4 4 5 5 5 5

A = replacePattern(A,[5,4,4,5],[5,5,5,5])

A = 1×23

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 4 4 4 5 5 5 5

function out = replacePattern(array,pat,rep)
for idx = 1:length(array)-length(pat)+1
    if all(array(idx:idx+length(pat)-1) == pat)
        array(idx:idx+length(pat)-1) = rep;
    end
end

out = array;
end

Answer 3

[the cyclist]

Here is an absolutely terrible, obfuscated way to do this:

A = [5,5,5,5,5,4,5,5,5,5,4,4,5,5,5,5,4,4,4,5,5,5,5];

SA = char(A);

S = {char([5 4 5]);
     char([5 4 4 5])};

R = {char([5 5 5]);
     char([5 5 5 5])};

for nr = 1:numel(R)
    SA = strrep(SA,S{nr},R{nr});
end

A = SA - char(0)

A = 1×23

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 4 4 4 5 5 5 5

I racked my brain for a numeric equivalent to strrep, but I couldn't remember (or find) one.