How do I make the matrix match in size

Hi, I'm trying to do my homework assignment, but I have gotten multiple errors so far. I'm not sure how to make the matrix size agree, either how to ensure that the grid is comprised of 61 x 81. This is my code so far:

x = -4:0.1:4;
y= -3:0.1:3;
z = x.^2 - 2*x.*y + 3*y + 2;
plot3(x,y,z)
contour(x,y,z)

ASSIGNMENT INSTRUCTIONS >> Construct a 3-D surface plot of z = x.^2 - 2*x.*y + 3*y + 2. You must provide the following:

1. - Plot from -3 to 3 for x and -4 to 4 for y. Ensure that the grid is comprised of 61 x 81 data points.
2. - Display contour map in the same figure.
3. - Make sure that the shading for the surface is interpolated.
4. - Make the sure the overlaid mesh is visible, black and has line width of 1.5.

If someone would help me with the other bullet point too I would really appreciate. Please, show me the syntax.

Answer 1

[John BG]

Hi

answer 1:

x=linspace(-4,4,61)
y=linspace(-3,3,81)
[X,Y]=meshgrid(x,y)
Z=X.^2-2*X.*Y+3*Y+2
surf(Z)

answer 2

surfc(X,Y,Z)

or

figure(3);meshc(X,Y,Z)

answer 3

h=meshc(X,Y,Z)

the handle to the surface properties is

h(1) 
=
 Surface with properties:

         EdgeColor: 'flat'
         LineStyle: '-'
         FaceColor: [1 1 1]
      FaceLighting: 'none'
         FaceAlpha: 1
             XData: [81x61 double]
             YData: [81x61 double]
             ZData: [81x61 double]
             CData: [81x61 double]

    Show all properties
            AlignVertexCenters: 'off'
                     AlphaData: 1
              AlphaDataMapping: 'scaled'
               AmbientStrength: [1x1 double]
                    Annotation: [1x1 matlab.graphics.eventdata.Annotation]
              BackFaceLighting: 'reverselit'
                  BeingDeleted: 'off'
                    BusyAction: 'queue'
                 ButtonDownFcn: ''
                         CData: [81x61 double]
                  CDataMapping: 'scaled'
                     CDataMode: 'auto'
                   CDataSource: ''
                      Children: []
                      Clipping: 'on'
                     CreateFcn: ''
                     DeleteFcn: ''
               DiffuseStrength: [1x1 double]
                   DisplayName: ''
                     EdgeAlpha: 1
                     EdgeColor: 'flat'
                  EdgeLighting: 'flat'
                     FaceAlpha: 1
                     FaceColor: [1 1 1]
                  FaceLighting: 'none'
                   FaceNormals: [80x60x3 double]
               FaceNormalsMode: 'auto'
              HandleVisibility: 'on'
                       HitTest: 'on'
                 Interruptible: 'on'
                     LineStyle: '-'
                     LineWidth: [1x1 double]
                        Marker: 'none'
               MarkerEdgeColor: 'auto'
               MarkerFaceColor: 'none'
                    MarkerSize: 6
                     MeshStyle: 'both'
                        Parent: [1x1 Axes]
                 PickableParts: 'visible'
                      Selected: 'off'
            SelectionHighlight: 'on'
      SpecularColorReflectance: 1
              SpecularExponent: 10
              SpecularStrength: [1x1 double]
                           Tag: ''
                          Type: 'surface'
                 UIContextMenu: []
                      UserData: []
                 VertexNormals: [81x61x3 double]
             VertexNormalsMode: 'auto'
                       Visible: 'on'
                         XData: [81x61 double]
                     XDataMode: 'manual'
                   XDataSource: ''
                         YData: [81x61 double]
                     YDataMode: 'manual'
                   YDataSource: ''
                         ZData: [81x61 double]
                   ZDataSource: ''

by 'shading of the surface' I understand

    h(1).EdgeColor='interp'

answer 4

the handle to the contour is

   h(2)
   = 
    Contour with properties:

      LineColor: 'flat'
      LineStyle: '-'
      LineWidth: 1.500000000000000
           Fill: 'off'
      LevelList: [-10 0 10 20 30 40 50]
          XData: [81x61 double]
          YData: [81x61 double]
          ZData: [81x61 double]

    Show all properties
              Annotation: [1x1 matlab.graphics.eventdata.Annotation]
            BeingDeleted: 'off'
              BusyAction: 'queue'
           ButtonDownFcn: ''
                Children: []
                Clipping: 'on'
           ContourMatrix: [2x469 double]
               CreateFcn: ''
               DeleteFcn: ''
             DisplayName: ''
                    Fill: 'off'
        HandleVisibility: 'on'
                 HitTest: 'on'
           Interruptible: 'on'
            LabelSpacing: 144
               LevelList: [-10 0 10 20 30 40 50]
           LevelListMode: 'auto'
               LevelStep: 10
           LevelStepMode: 'auto'
               LineColor: 'flat'
               LineStyle: '-'
               LineWidth: 1.500000000000000
                  Parent: [1x1 Axes]
           PickableParts: 'visible'
                Selected: 'off'
      SelectionHighlight: 'on'
                ShowText: 'off'
                     Tag: ''
                TextList: [-10 0 10 20 30 40 50]
            TextListMode: 'auto'
                TextStep: 10
            TextStepMode: 'auto'
                    Type: 'contour'
           UIContextMenu: []
                UserData: []
                 Visible: 'on'
                   XData: [81x61 double]
               XDataMode: 'manual'
             XDataSource: ''
                   YData: [81x61 double]
               YDataMode: 'manual'
             YDataSource: ''
                   ZData: [81x61 double]
             ZDataSource: ''

the contour line width can be changed with

    h(2).LineWidth=1.5

Regarding the color request, I am not sure whether the 'overlaid mesh' comment means the color of the actual figure, that you can change color altering

h(1).FaceAlpha     % default 1
h(1).FaceColor:    % default [1 1 1]
h(1).FaceLighting  % default 'none'

or the color of the contours, that you can change with

h(2).ContourMatrix

If you find this answer of any help solving your question, please click on the thumbs-up vote link,

thanks in advance

John

[e-mail]

Answer 2

[James Tursa]

Instead of using x and y in your z equation directly, first make a grid of x and y values. E.g.,

[X Y] = ndgrid(x,y);

Then you can use these X and Y grids to generate the Z values:

Z = X.^2 - 2*X.*Y + 3*Y + 2;

Now you have what you need for the downstream stuff.