How to mark certain points in my surface or pcolor plot?

I had the following plot which I need to mark points with specific values in Z=1:

pcolor(xx,yy,Z) and surf(xx,yy,Z).

But when I use the command :

shading interp

hold on

xx = get(lambda1,'xxdata') ;

yy = get(lambda1,'yydata') ;

Z = get(lambda1,'Zdata') ;

ind = Z==1;

plot3(xx(ind),yy(ind),1,'yp')

text(xx(ind),yy(ind),'Z = 1','fontweight','bold','color','b')

contour(xx,yy,Z,[1 1],'magenta','linewidth',4)

hold off

It doesn't work in marking the points which Z=1. It's there anyone can help me with that problem?

[darova]

Try contour3

contour3(xx,yy,Z,[1 1])

[Jun Xiao]

I tried this. But still no improvement of my plot, with the error: Error using handle.handle/get

Invalid or deleted object.

[darova]

Impossible. Where?!

[Jun Xiao]

I don't know. The error occurs after I add the command which attempt to mark points of the plot after the surface/pcolor command. And matlab has no document of handle.handle/get.