is_handle_valid — Check wether a set of graphic handles is still valid.
isValid = is_handle_valid(h)
is_handle_valid function tests wether a set of graphic handle
is still valid. A valid handle is a handle which has not been deleted.
The result, isValid, is a boolean matrix such as
isValid(i,j) is true if
h(i,j) is valid and false otherwise.
// check that current objects are valid
is_handle_valid([gcf(), gca(), gce()])
// create 11 polylines
plot([0:10; 0:10; 0:10], [0:10; 0:0.5:5; 0:2:20]);
// check polylines validity
axes = gca();
polylines = axes.children(1).children
is_handle_valid(polylines)
// delete some polylines
delete(polylines(3:7));
// print validity
is_handle_valid(polylines)