MATLAB coder error：Unable to determine that every element of cell is assigned before this line

WHEN USING MATLAB CODER TO GENERATE C CODE,

I faced up with the error :"Unable to determine that every element of 'region{:}' is assigned before this line. "

I checked the guidance and set the code into form the same as which in the guidance:

region = cell(rlen,1);
for rn = 1:rlen
    region{rn}=[0,0];
end

But the error still in. Anyone can help?

Thanks a lot.

Followed as part of my code:

region = cell(rlen,1);
        for rn = 1:rlen
            region{rn}=[0,0];
        end 
       %% region init

        regionr = int16(zeros(length(region),1));
        for ii = 1:length(region)
            regionr(ii) = int16(sqrt(double(region{ii}(1)^2 +double(region{ii}(2)^2))));
            %% error occured here:
            %%Unable to determine that every element of 'region{:}' is assigned before this line.
        end

[KSSV]

The given code do not throw any error.

[wu you]

I met with the error while using the tool: matlab coder. It works normally in matlab environment.

It's my fault not to clarify it at first. The question has been re-edited.

[Jan]

The code can be simplified:

% ------------------------------------
region = cell(rlen,1);
for rn = 1:rlen
    region{rn} = [0,0];
end

% Shorter and faster:
region = cell(rlen, 1);
region(:) = {[0, 0]};

% ------------------------------------
regionr = int16(zeros(length(region),1));

% Faster:
regionr = zeros(rlen, 1, 'int16');

% ------------------------------------
for ii = 1:length(region)
   regionr(ii) = int16(sqrt(double(region{ii}(1)^2 +double(region{ii}(2)^2))));
end

% Easier: region{ii} is a double already. You cast region{ii}(2)^2 to a
% double, add it to region{ii}(1)^2 and cast the result to a double again.
% This is confusing only. Leaner:
for ii = 1:rlen
   regionr(ii) = int16(sqrt(region{ii}(1)^2 + region{ii}(2)^2));
end

But I do not see an error also.

Answer 1

[wu you]

I tried the 3rd method provided in the guidance, it works. Just like code below:

region1 = cell(rlen,1);
region = coder.nullcopy(region1);
for rn = 1:rlen
    region{rn}=f{rn+left};
end

But i still wonder why the 1st method i used does not work.