How can I make a color map plot in matlab

Question

I have some data  a function of two parameters  stored in a matlab format  and I d like to use matlab to plot it  Once I read the data in  I use mesh   to make a plot  My mesh   plot gives me the the value of the function as a color and a surface height  like this     What matlab plotting function should I use to make a 2D mesh plot where the dependent variable is represented as only a color  I m looking for something like pm3d map in gnuplot

User · Answer

Note that both pcolor and  surf   view 2   do not show the last row and the last column of your 2D data   On the other hand  using imagesc  you have to be careful with the axes  The surf and the imagesc examples in gevang s answer only  almost -- apart from the last row and column  correspond to each other because the 2D sinc function is symmetric   To illustrate these 2 points  I produced the figure below with the following code    x  y    meshgrid 1 10 1 5   z        x  3   y  3   subplot 3 1 1  imagesc flipud z    axis equal tight  colorbar set gca   YTick   1 5   YTickLabel   5 -1 1   title  imagesc    subplot 3 1 2  surf x y z  EdgeColor   None    view 2   axis equal tight  colorbar title  surf with view 2     subplot 3 1 3  imagesc flipud z    axis equal tight  colorbar axis  0 5 9 5 1 5 5 5   set gca   YTick   1 5   YTickLabel   5 -1 1   title  imagesc cropped    colormap jet     As you can see the 10th row and 5th column are missing in the surf plot   You can also see this in images in the other answers    Note how you can use the  set gca   YTick       and Xtick  command to set the x and y tick labels properly if x and y are not 1 1 N   Also note that imagesc only makes sense if your z data correspond to xs and ys are  each  equally spaced  If not you can use surf  and possibly duplicate the last column and row and one more   end end   value -- although that s a kind of a dirty approach

User · Answer

By default mesh will color surface values based on the  default  jet colormap  i e  hot is higher   You can additionally use surf for filled surface patches and set the  EdgeColor  property to  None   so the patch edges are non-visible      X Y    meshgrid -8  5 8   R   sqrt X  2   Y  2    eps  Z   sin R   R     surface in 3D figure  surf Z  EdgeColor   None        2D map  You can get a 2D map by switching the view property of the figure     2D map using view figure  surf Z  EdgeColor   None    view 2               or treating the values in Z as a matrix  viewing it as a scaled image using imagesc and selecting an appropriate colormap      using imagesc to view just Z figure  imagesc Z    colormap jet        The color pallet of the map is controlled by colormap map   where map can be custom or any of the built-in colormaps provided by MATLAB       Update Refining the map  Several design options on the map  resolution  smoothing  axis etc   can be controlled by the regular MATLAB options  As  Floris points out  here is a smoothed  equal-axis  no-axis labels maps  adapted to this example         figure  surf X  Y  Z  EdgeColor    None    facecolor    interp    view 2   axis equal   axis off

User · Answer

I also suggest using contourf Z   For my problem  I wanted to visualize a 3D histogram in 2D  but the contours were too smooth to represent a top view of histogram bars   So in my case  I prefer to use jucestain s answer  The default shading faceted of pcolor   is more suitable  However  pcolor   does not use the last row and column of the plotted matrix  For this  I used the padarray   function   pcolor padarray Z  1 1  0  post      Sorry if that is not really related to the original post

User · Answer

gevang s answer is great  There s another way as well to do this directly by using pcolor  Code    X Y    meshgrid -8  5 8   R   sqrt X  2   Y  2    eps  Z   sin R   R  figure  subplot 1 3 1   pcolor X Y Z    subplot 1 3 2   pcolor X Y Z   shading flat  subplot 1 3 3   pcolor X Y Z   shading interp    Output     Also  pcolor is flat too  as show here  pcolor is the 2d base  the 3d figure above it is generated using mesh

[matlab] How can I make a "color map" plot in matlab?

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