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Unexpected behaviour from ishandle()

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Temu Gautama
Temu Gautama 2019-11-22
编辑： Stephen23 2019-11-22
Hi,
In a script, I was checking the existence of a plot handle to either make a new plot or to change the x/y data. Surprisingly this didn't work by initially setting the plot handle to []. Reason:
>> ishandle( [] )
ans =
[]
which sort of makes sense.
However, my next step was to initialise the plot handle to 0, which also didn't work, and this was the real surprise:
>> ishandle( 0 )
ans =
1
Even though
>> ishandle( 1 )
ans =
0
Does anybody why zero would be a valid graphics or Java object handle?
Thanks,
Temu

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采纳的回答

Stephen23
Stephen23 2019-11-22
编辑：Stephen23 2019-11-22
On MATLAB versions prior to R2016b zero is the handle to the graphics root (i.e. the parent of all graphics figures):
https://www.mathworks.com/help/matlab/graphics-objects.html
For compatilbility using zero is still permitted in later versions.
https://www.mathworks.com/help/matlab/ref/groot.html

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