I am trying to make these 3 plots

if you see eqution 12.1-31, I made a Matlab code to genterte the figure 12.1-1. I tried but not correct

here is my code

clc;clear all;

n=100000;
alphat=1;
y_b=linspace(0,1);
% y_b=.1
for j=1:length(y_b)
    sum_D=0;
    for i=1:n
        sum_D=sum_D+(((-1)^(i-1))/(((i-1)+0.5)*pi))*exp(-((i-1)+0.5)^2*pi^2*alphat)*cos((i-1)+0.5)*pi*y_b(j);
    end
    F(j)=2*sum_D;
end
plot(y_b,F);grid on;

[Walter Roberson]

How does this differ from https://www.mathworks.com/matlabcentral/answers/1662610-i-am-trying-to-generate-these-3-plots?s_tid=srchtitle ?

Where are you taking into account the analysis I posted in https://www.mathworks.com/matlabcentral/answers/1662610-i-am-trying-to-generate-these-3-plots#answer_909164 in which I showed that your code is creating strictly linear responses?