Out of memory. The likely cause is an infinite recursion within the program. Error in polyfit (line 3) p = polyfit(x,y,2);

Hello I get this error when trying to run my code," Out of memory. The likely cause is an infinite recursion within the program." Any idea on how to fix this? My code is below.

t = [0:1:20];

Ca = [10,9.090909,8.333333,7.692308,7.142857,6.666667,6.25,5.882353,5.555556,5.263158,5,4.761905,4.545455,4.347826,4.166667,4,3.846154,3.703704,3.571429,3.448276,3.333333];

logCa = log(Ca);

coeff = polyfit(t,logCa,1)

Answer 1

[Mathieu NOE]

No issue so far on my R2020b

copy pasted your data in my demo code and worked without issue :

clc
clearvars

%  data
x = [0:1:20];
Ca = [10,9.090909,8.333333,7.692308,7.142857,6.666667,6.25,5.882353,5.555556,5.263158,5,4.761905,4.545455,4.347826,4.166667,4,3.846154,3.703704,3.571429,3.448276,3.333333];
y = log(Ca);

% Fit a polynomial p of degree "degree" to the (x,y) data:
degree = 1;
p = polyfit(x,y,degree);

% Evaluate the fitted polynomial p and plot:
f = polyval(p,x);
eqn = poly_equation(flip(p)); % polynomial equation (string)
Rsquared1 = my_Rsquared_coeff(y,f); % correlation coefficient

figure(1);plot(x,y,'o',x,f,'-')
legend('data',eqn)
title(['Data fit - R squared = ' num2str(Rsquared1)]);


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

function Rsquared = my_Rsquared_coeff(data,data_fit)
    % R2 correlation coefficient computation
    
    % The total sum of squares
    sum_of_squares = sum((data-mean(data)).^2);
    
    % The sum of squares of residuals, also called the residual sum of squares:
    sum_of_squares_of_residuals = sum((data-data_fit).^2);
    
    % definition of the coefficient of correlation is
    Rsquared = 1 - sum_of_squares_of_residuals/sum_of_squares;
    
    
end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function eqn = poly_equation(a_hat)
eqn = " y = "+a_hat(1);
for i = 2:(length(a_hat))
    if sign(a_hat(i))>0
        str = " + ";
    else
        str = " ";
    end
    if i == 2
        eqn = eqn+str+a_hat(i)+"*x";
    else
        eqn = eqn+str+a_hat(i)+"*x^"+(i-1)+" ";
    end
end
eqn = eqn+" ";
end