This example shows how to define a new histogram representation with a COMIS routine.

The routine derr.f
                                                                                        
      Subroutine Derr(Id)                                                                                               
      Character*80 Chtitl                                                                                               
      Real Errx(2)                                                                                                      
      Real Erry(2)                                                                                                      
      Real Errz(2)                                                                                                      
1     Call Hgive(Id,Chtitl,Nx,Xmin,Xmax,Ny,Ymin,Ymax,Nwt,Idb)                                                    
      If (Ny.Eq.0) Return                                                                                               
      Zmin = Hcxy(1,1,1)                                                                                                
      Zmax = Zmin                                                                                                       
2     Do i=1,Nx                                                                                                  
         Do j=1,Ny                                                                                                      
            Z   = Hcxy(i,j,1)                                                                                           
            E   = Hcxy(i,j,2)                                                                                           
            Ze1 = Z-E                                                                                                   
            Ze2 = Z+E                                                                                                   
            If (Ze1.Lt.Zmin) Zmin=Ze1                                                                                   
            If (Ze1.Gt.Zmax) Zmax=Ze1                                                                                   
            If (Ze2.Lt.Zmin) Zmin=Ze2                                                                                   
            If (Ze2.Gt.Zmax) Zmax=Ze2                                                                                   
         Enddo                                                                                                          
      Enddo                                                                                                             
3     Call Hplfr3(Xmin,Xmax,Ymin,Ymax,Zmin,Zmax,30.,30.,'FWB')                                                   
      Dx = (Xmax-Xmin)/Nx                                                                                               
      Dy = (Ymax-Ymin)/Ny                                                                                               
      X  = Xmin+Dx/2.                                                                                                   
4     Do i=1,Nx                                                                                                  
         Y = Ymin+Dy/2.                                                                                                 
         Do j=1,Ny                                                                                                      
            Z       = Hcxy(i,j,1)                                                                                       
            E       = Hcxy(i,j,2)                                                                                       
            Errx(1) = X                                                                                                 
            Errx(2) = Errx(1)                                                                                           
            Erry(1) = Y                                                                                                 
            Erry(2) = Erry(1)                                                                                           
            Errz(1) = Z-E                                                                                               
            Errz(2) = Z+E                                                                                               
            Call Ipm3(1,X,Y,Z)                                                                                          
            Call Ipl3(2,Errx,Erry,Errz)                                                                                 
            Y = Y+Dy                                                                                                    
         Enddo                                                                                                          
         X = X+Dx                                                                                                       
      Enddo                                                                                                             
      End                                                                                                               

How to use derr.f
                                                                                         
      hi/file 0 pawhists.hbook                                                                                          
      hrin *                                                                                                            
5     SET MTYP 20                                                                                                
5     CALL DERR.F(200)                                                                                           

1. Retrieve informations about the histogram.
2. Loop over all the bins to find the minimum and the maximum taking care of the errors.
3. Draw the 3D frame.
4. Loop over all the bins and draw the error bars.
5. Set the marker type and invoke the derr routine.