title: Plotting multiple gridlines and give seperate labels in Mathematica
body: <p>I am trying to make the following plot:</p>
  
  <pre><code>Pars = {ep -&gt; 0.5, f1p -&gt; 0.3, f2p -&gt; 0.1, dp -&gt; 0.05, q -&gt; 0.1, 
     en -&gt; 0.4, d -&gt; 0.1, Q -&gt; 0.1, f2n -&gt; 0.3, f1n -&gt; 0.4, a -&gt; 0.05, 
     N1 -&gt; 0.5, N2 -&gt; 0.5}; #Parameters
  
  PlotREq1 = 
    Plot[R = S /. Pars, {S, 0, 0.9375}, 
     PlotRange -&gt; {{0, 3.5}, {0, 2}}, PlotStyle -&gt; {Red, Thick, Dashed},
      GridLines -&gt; {{0.9375}, {}}];  
  PlotREq2 = 
    Plot[R = (a + d)/(en f1n) /. Pars, {S, 0.9375, 1.4375}, 
     PlotRange -&gt; {{0, 3.5}, {0, 2}}, PlotStyle -&gt; {Red, Thick, Dashed},
      GridLines -&gt; {{1.4375}, {}}];
  PlotREq3 = 
    Plot[R = ((a + d) (f1p - f2p))/(en (f1p f2n - f1n f2p)) /. Pars, {S,
       1.4375, 2.3}, PlotRange -&gt; {{0, 3.5}, {0, 2}}, 
     PlotStyle -&gt; {Red, Thick, Dashed}, GridLines -&gt; {{2.3}, {}}];
  Show[PlotREq1, PlotREq2, PlotREq3]
  </code></pre>
  
  <p>However, only the first gridline shows up and the other two vertical lines at 1.4375 and 2.3 do not appear. Also, can anyone suggest a way to label the gridlines? I tried to insert a axeslabel within the Gridline function as: <code>Gridlines -&gt; {{{0.9375},{}}, AxesLabel -&gt; {"R",""}}</code> but it does not seem to work.</p>