title: Dipol moment integral
body: <p>I would like this calculate dipol moment integral</p>
  <p><img src="https://i.stack.imgur.com/5PJ3X.png" alt="enter image description here" /></p>
  <p>This is my code:</p>
  <pre><code>fi_1 = @(r) (1/(2*pi)^(0.5))*exp((1i*r)./R); % wave function the fist state
  fi_3 = @(r) (1/(2*pi)^(0.5))*exp((1i*3*r)./R); % wave function the third state
  
  fun_13 =  @(r) fi_1.*e*r.*fi_3; %dipol moment funstion
  
  d_13 = integral(fun_13,0,R_1);
  </code></pre>
  <p>However, it returns this error:</p>
  <p><img src="https://i.stack.imgur.com/wG0sv.png" alt="enter image description here" /></p>