Re: [matplotlib-devel] Contour and Vector Plots

[Helge A. <av...@ii...>]

John Hunter <jdh...@ac...> writes:

| 
| Do you have any thoughts on how we might do labels with your code?

2 ways:

1) automatically: define a coarser(user defined coarseness) mesh on
   the function to be labelled, and add the labels in the vertices of
   this mesh. the angle of each label can easily be found from the
   closest contour line segment. this method avoids clusters of labels
   effectively, but will not be good in areas with high variability.

2) manually: let the user point and click on contours, I implemented
   this for use with gist that you could take a look at (clabel below).
   matlab also does this, and I think this is the best way for real
   publication quality. I have never seen automatic routines that do
   labelling well. TECPLOT is close but not quite there.

   I also attached a routine to do this for 2D stretched coordinates (see
   the contour plots with labels on
      http://www.ii.uib.no/~avle/python.html 
   for examples) which is called vclabel

| 
| If we decide to go with your routines, at least for the time being
| until we can "do it right", would you be willing to contribute your
| code to matplotlib under the matplotlib license (PSF inspired, free
| for commercial and noncommercial reuse)?

sure, no problem.

Helge




def clabel(z,clevels,opa=1,col='black',meth='std',digits=1):
    """
    clabel(z,clevels,opa=1,col='black')
    
    At the point where the mouse is clicked, print the contour level
    from clevels that are closest to the interpolated value in this
    point. Meant to be useful for labeling contour lines manually...
    
    optional arguments:
    opa=0 : Transparent text.
    opa=1 : Erase background under label
    col='white'  : text color.
    meth= 'std'   bilinear interpo on a std grid, might give error near coast
          'grid'  values not given cellcentered but on corners of cells. 
          'bigrid' values taken from a bilinearly interpol fine mesh from
	  futil.contour
          'cell'  takes value from cell directly

    Helge Avlesen <av...@ii...>
    
    """
    
    print """
    Insert contour levels by left clicking, middle button display
    values, right button finishes.
    """
    
    button=0
    while button<>3:    
        mus=gist.mouse()                   
        button=mus[9]

	if meth=='bigrid':
	    i=int(2*mus[0])+1 ; j=int(2*mus[1])+1
	    x=2*mus[0]-i+1     ;  y=2*mus[1]-j+1
	elif meth=='std':
	    i=int( mus[0] );  j=int( mus[1] )
	    x=mus[0]-i     ;  y=mus[1]-j
	elif meth=='grid':	    
	    xm=mus[0]+0.5 ; ym=mus[1]+0.5
	    i=int( xm );  j=int( ym )
	    x=xm-i     ;  y=ym-j
        elif meth=='cell':
            print mus[0], mus[1]
            i=int(round(mus[0])) ; j=int(round(mus[1]))

        if meth=='cell':
            val=z[i,j]
            print val,i,j
        else:
            # bilinear interpolation to find value        
            a00=z[i,j] 
            a10=z[i+1,j]-a00 
            a01=z[i,j+1]-a00 
            a11=z[i+1,j+1]-(a00+a10+a01) 
            val=a00 + a10*x + a01*y + a11*x*y
            print val,i,j,x,y            

        if button==1:                    
            # compare this value to the selected levels
            diff= abs( clevels-val )  

            # use the closest
            label=fpformat.fix( clevels[  Numeric.argmin(diff) ], digits )

            gist.plt(label, mus[0], mus[1], opaque=opa, tosys=1, \
                     height=8, justify="CH", color=col )



def vclabel(z,sx,sy,clevels,opa=1,col='black',digits=1):
    """
    manual(z,clevels,opa=1,col='black')
    
    At the point where the mouse is clicked, print the contour level
    from clevels that are closest to the interpolated value in this
    point. Meant to be useful for labeling contour lines manually...

    sx[i,j],sy[i,j] is the x,z coordinate of point z[i,j]. if [:,1]
    denotes the top layer, [:,kb-1] the bottom (common in
    oceanography) j_is_down will be true. (z is always positive in
    the upward direction, but the indice j may go downwards)
    
    optional arguments:
    opa=0 : Transparent text.
    opa=1 : Use background color for text.
    col='white'  : text color.
    digits: number of decimals in label

    Helge Avlesen <av...@ii...>
    
    """
    
    print """
    Insert contour levels by left clicking, middle button display
    depth, right button finishes.
    """
    kb=z.shape[1]
    im=z.shape[0]

    j_is_down=0    
    if sy[0,0]>sy[0,1]:
        j_is_down=1
    
    button=0
    while button<>3:
        mus=gist.mouse()
        button=mus[9]
       
	# bisection search for the indices
        i=hbisect( sx[:,0], mus[0] )
        if i<0 or i>im-1:
            print 'outside:',i
            continue
        
        x=(mus[0]-sx[i,0])/(sx[i+1,0]-sx[i,0])
        
        if j_is_down:
            finn=hbisect( (1.-x)*sy[i,::-1] + x*sy[i+1,::-1] , mus[1] )
            j=kb-2-finn
            if finn<0 or finn>kb-1:
                print 'outside',i,finn
                continue
       
            xa=Numeric.array((sx[i,j+1]+x*(sx[i+1,j+1]-sx[i,j+1]),\
                              sy[i,j+1]+x*(sy[i+1,j+1]-sy[i,j+1])))
            
            if mus[1]-xa[1]<0:
                print 'below'
                continue
            
            xb=Numeric.array((sx[i,j]+x*(sx[i+1,j]-sx[i,j]),\
                              sy[i,j]+x*(sy[i+1,j]-sy[i,j])))
        
            y=(((mus[0]-xa[0])**2 + (mus[1]-xa[1])**2 )\
               /((xb[0]-xa[0])**2 + (xb[1]-xa[1])**2 ))**0.5
                
            # bilinear interpolation to find value
        
            a1=z[i,j+1] 
            a2=z[i+1,j+1]-a1 
            a3=z[i,j]-a1	
            a4=z[i+1,j]-(a1+a2+a3) 
            val=a1 + a2*x + a3*y + a4*x*y
        else:
            print 'increasing j upwards not yet implemented'
            continue
            
        print 'x,y=',x,y,' i,j=',i,j, 'val=',val

        if button==1:                    
            # compare this value to the selected levels
            diff= abs( clevels-val )  

            # use the closest
            label=fpformat.fix( clevels[  Numeric.argmin(diff) ], 1)

            if opa==1:
                label=' '+label+' '

            gist.plt(label, mus[0], mus[1], opaque=opa, tosys=1, \
                     height=8, justify="CH", color=col )