Matlab code generator generates a error stating "Undefined function or variable. The first assignment to a local variable determines its class."

Hello,

When i am trying to generate a C code from Matlab code generat the following error occurs.

" Undefined function or variable 'ext'. The first assignment to a local variable determines its class"

My Code is given below :

function extremePoints()

state = [0 10 20 50 30 20 60 70 60 10]

dSOC = diff(state);

sgn = sign(dSOC);

ext(1)=0;

j=2;

%finding extremes of state

for i=2:length(state)-1

if sgn(i-1) ~= sgn(i)

ext(j)=state(i);

j=j+1;

end

end

ext(j)=state(end)

end

I have used coder.varsize, but it dosent work or i have not used efficiently. Please solve the problem.

[infinity]

It is clear that ext was not declared as any type of variable (scaler, vector, matrix, etc). I guess you want to use it as a vector. So, why don't you declare ext as a vector with specific lenght? for example,

 ext = zeros(1,length_of_ext); 

[Mohan Gopal Tripathi]

hello,

it is working, thanks for the help. Also, if I want to use it as resizeable matrix, what must i do. I dont know the limit if the matrix and it changes in every different inputs.

[infinity]

To handle the problem of unknown lenght of ext, you can first assume ext as a vector of a large length of NaN, for example, ext = NaN(1,1000). ext finally contains your desire values and some NaN that can be treated as non-number.

[Walter Roberson]

It is possible to create resizeable matrices, but it involves memory allocation routines which can lead to challenges for real time work. It is typically better to use a different approach:

decide on a maximum size that will not be exceeded unless the program gets rebuilt. Use the size() (not length()) of an input as the size for zeros() to initialize the array. But also add an assert() just before that that checks that the size is no more than the limit you are willing to impose.

Coder knows how to use the assert() to allocate maximum stack sizes if needed, for efficient allocation and ability to confirm that the maximum stack will not exceed the available memory of the processor.