How to plot a function ?

Question

Alexandru Stefan 2014-3-17

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/121864-how-to-plot-a-function

评论： Alexandru Stefan 2014-3-19

Helli, i'm a newbie in mathlab and i try for hours to make the program below, please would you explained me how to begin or make the program and write the code to see where i make some mistake.

Write a program that recieve as arguments two real numbers a and b with a>0 and b∈(0,1) and who represent graphic in cartesian coordinate function f:[0,2]->R.

       { (a*x)/(x^2+b), x∈[0,1]
f(x)=  {
       { ln(x^2-3*x+3), x∈(1,2]

with dashed line and black color. The program display an error message if the requirements about arguments are not respected.

Thank You!!

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Answer 1

Carlos 2014-3-17

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https://ww2.mathworks.cn/matlabcentral/answers/121864-how-to-plot-a-function#answer_128738

编辑：Carlos 2014-3-17

在 MATLAB Online 中打开

Some ideas here

function y=new(a,b)
if(a<0)
  disp('a must be bigger than zero');
end
if(b<0||b>1)
  disp('a must be bigger than zero and smaller than 1');
end
x=0:0.1:2;
y=zeros(1,length(x));
for k=1:length(x)
  if (x(k)<1)
  y(k)=(a*x(k))/(x(k)^2+b);
  else
  y(k)=log(x(k)^2-3*x(k)+3);
  end
end
plot(x,y)

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Carlos 2014-3-17

My bad, you are right.

Alexandru Stefan 2014-3-19

Thank you, both were really helpful.

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Answer 2

Niklas Nylén 2014-3-17

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/121864-how-to-plot-a-function#answer_128739

在 MATLAB Online 中打开

 function fx = myFunction(a,b)
 x=0:0.1:2; % Create the x vector with step size 0.1
 fx = zeros(size(x)); % Initialize the function output fx with zeros
 % Make the calculation for when x<=1
 index = x <= 1; % Creates a logical vector with 0's and 1's
 % Calculate f(x) for the indices of x which fulfill the previous logical statement
 fx(index) = (a.*x(index))./(x(index).^2+b); 
 % Use the second equation when x > 1
 index = x > 1;
 fx(index) = log(x(index).^2-3.*x(index)+3);
 figure; 
 plot(x,fx)