%a cockrach=importdata('cockroach_population.xlsx'); num_cockrach=cockrach.data; days=num_cockrach(:,1); cockraches=num_cockrach(:,2); %b ylin=cockraches; xlin=log(days); [a0,a1,r2] = linreg(xlin,ylin); p=polyfit(days,cockraches,2); alpha=(exp(1)).^a0; Beta=a1; text1=sprintf('parabola-cockraches rate: cockraches= %.2fx^2+%.2fx+%.2f',p); %c exponential_curve= alpha.*exp(1).^(Beta.*days); text2=sprintf('exponential-cockraches rate: cockraches= %.2fe^%.2fx\n',alpha, Beta); figure plot(days,cockraches,'b.'); hold on plot(days,polyval(p,days),'r-','LineWidth',3); plot(days,exponential_curve,'g-','LineWidth',3) title('numbers of cockraches vs times(days)'); xlabel('cockraches'); ylabel('days'); legend('unlinearised',text1,text2)

my graph won't show the exponential graph as the alpha value is 0, can someone help fix this problem?

3 次查看（过去 30 天）

Elisa 2024-9-13

评论： Torsten 2024-9-13

cockrach=importdata('cockroach_population.xlsx');

num_cockrach=cockrach.data;

days=num_cockrach(:,1);

cockraches=num_cockrach(:,2);

ylin=cockraches;

xlin=log(days);

[a0,a1,r2] = linreg(xlin,ylin);

p=polyfit(days,cockraches,2);

alpha=(exp(1)).^a0;

Beta=a1;

text1=sprintf('parabola-cockraches rate: cockraches= %.2fx^2+%.2fx+%.2f',p);

exponential_curve= alpha.*exp(1).^(Beta.*days);

text2=sprintf('exponential-cockraches rate: cockraches= %.2fe^%.2fx\n',alpha, Beta);

figure

plot(days,cockraches,'b.');

hold on

plot(days,polyval(p,days),'r-','LineWidth',3);

plot(days,exponential_curve,'g-','LineWidth',3)

title('numbers of cockraches vs times(days)');

xlabel('cockraches');

ylabel('days');

legend('unlinearised',text1,text2)

Elisa 2024-9-13

I think i found the problem, thank you！

Torsten 2024-9-13

It's not wrong, but better use exp(x) instead of exp(1).^x in your code.

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