Manipulate code creates error messages when file is opened

Question

When I open the file containing the following code I get a series of error messages. Once I evaluate the cell with the code the error messages disappear. What is Mathematica doing when it opens a file, or how can avoid creating this problem for myself in the future?

 econmagic1[ ds_, di_, ss_, si_  ] := (
  (* begin equilibrium calculation *)

 A = { { 1, - 1 ds }, { 1, - ss } };
  CC = Inverse[ A ].{ di, si };

  Manipulate[
   (* begin grid layout*)
   Grid[{

     (* begin first row *)
     {Show[

       (* begin initial supply curve *)

   Plot[ ( 1 / ss ) ( x - si ), {x, 0, Part[ CC, 1] }, 
    PlotStyle -> { Red, Dashed },      
    PlotLegends -> { "Initial Supply Set"}],

       (* begin initial demand curve *)

   Plot[ ( 1 / ds ) x + (  - di / ds) , {x, 0, di },  
    PlotStyle -> Dashed,  PlotLegends -> { "Initial Demand Set"} ],

       (* begin demand curve *)

   Plot[ ( 1 / ds ) ( x - et ) + (  - di / ds) , {x, 0, 
     di + et},  PlotLegends -> { "Demand Set"} ],

       (* begin supply curve *)

   Plot[ ( 1 / ss ) ( x - si ), {x, 0, 
     Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
        si }, 1 ]}, PlotStyle -> Red, 
    PlotLegends -> { "Supply Set"}],

       (* begin horizontal for equilibrium *)

   Plot[Part[ 
     Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, si }, 
     2 ],  {x, 0, 
     Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
        si }, 1 ]},  PlotStyle -> { Dashed, Thick } ],

       (* begin filling for consumer surplus *)

   Plot[{  ( 1 / ds ) ( x - et ) + (  - di / ds), 
     Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
        si }, 2 ] }, {x, 0, 
     Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
        si }, 1 ]}, Filling -> 1 -> {2}, 
    FillingStyle -> Directive[ Opacity[ 0.1 ], Blue ] ],

       (* begin filling for producer surplus *)

   Plot[{  Part[ 
      Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, si }, 
      2 ],  ( 1 / ss ) ( x - si ) }, {x, 0, 
     Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
        si }, 1 ] }, Filling -> 1 -> {2}, 
    FillingStyle -> Directive[ Opacity[ 0.1 ], Red ] ],

       (* begin equilibrium point *)

   ListPlot[{ { 
      Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
         si }, 1 ], 
      Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
         si }, 2 ] } }, PlotStyle -> Black, 
    PlotLegends -> { "Equilibrium Point" }],

       (* begin dashed lines for market equilibrium *)     

   Graphics[{ Dashed, 
     Line[{ { 
        Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
           si }, 1 ], 0 }, { 
        Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
           si }, 1 ], 
        Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
           si }, 2 ]}}] }],

       AxesOrigin -> { 0, 0 }, 
   PlotRange -> { { 0, di + 10 }, { 0, (  - di / ds) + 10 }},   
   AxesLabel -> { "Quantity", "Price"}, ImageSize -> Large
   ]}, (* End Show *)

     (* begin second row *)
     { Grid[{

        (* 
    second row first column *)
        {"QD Price Intercept:" TraditionalForm[ - ( di + et ) / ds ],

         (* second row second column *)

     "QD Quantity Intercept:" TraditionalForm[ di + et ] },

        (* 
    third row first column *)
            {"QS Price Intercept:" TraditionalForm[ - si / ss ],

         (* third row second column *)

     "The equilibrium point is:"     TraditionalForm[ { 
        Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
           si }, 1 ], 
        Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
           si }, 2 ] } ] },

        (*  fourth row first column *)    
      {"Consumer Surplus:" TraditionalForm[( 
         1 / 2 ) ( (- di / ds ) - 
          Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ 
             di + et, si }, 2 ])  Part[ 
         Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
           si }, 1 ] ],

         (* fourth row second column *)

     "Producer Surplus:" If[

           (*  Does the Supply Curve Intersect the Price Axis *)
           ( - si / ss ) >= 0,

           (*  Supply Curve Intersects Price Axis *)

       TraditionalForm[ .5 ( 
          Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ 
              di + et, si }, 2 ] - ( - si / ss  ) ) ( 
          Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ 
             di + et, si }, 1 ] )],

           (* Supply Curve Does Not Intersect Price Axis *)
       TraditionalForm[ 0.5  ( Part[ 
            Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ di + et, 
              si }, 1 ] -  si  ) ( 
          Part[ Inverse[{ { 1, - 1 ds }, { 1, - ss } } ].{ 
             di + et, si }, 2 ] )]

       ] }
     },
   Alignment -> Left, Frame -> All, Spacings -> { 4, 1 } ]
   }
   }, Alignment -> Left],
   { { et, 0 },  -4.5, 25 } ]
   )

Answer 1

You are missing SaveDefinitions->True in your Manipulate. Therefore, when the notebook is opened, the functions in the calls to Plot are undefined and it pinks until you evaluate and restore the definitions.