check if figure exists whithout making it appear and using its figure number in findobj()

Hi,

I want to know if a figure exists, however without it ever appearing at the forefront (I thus cannot use simply the figure() function). The function findobj() is a good candidate to solve this problem, however I do not want to use the 'name' as the argument for the search, i.e. I do not want to do:

findobj('type','figure','name','mytitle')

but rather use the number of the figure used when the figure is created, using

figure(nbrfig)

Does something like the following code exists?

findobj('type','figure','NUMBER OF THE FIGURE',nbrfig)

I tried number, handle, ... instead of 'NUMBER OF THE FIGURE' but nothing works. Need help :) thanks.

[Jan]

It is not clear, what the "number of a figure" means.

Answer 1

[dpb]

Since the figure number handles are the integer number, all you really need to do then is use

ishandle(n)

for the desired number.

Or, I'm not seeing the problem...???

[rikki]

is there any way too store this figure in some variable so that i can do modification in that.for example ishandle(6) now hv to store in some variable to apply preprocessing technique.

[dpb]

A figure handle in HG2 is now a figure object as opposed to HG1 in which it was just a default integer that happened to represent a figure but there's no reason you can't retrieve said handle and store it in a variable.

Read about gcf and figure and general background on handle graphics.

[Mohamed Abdelhamid]

I noticed that if the figure hasn't been open before and its handle is stored in the workspace, then this statement would give an error. I suggest using the following:

exist('h') && ishandle('h')

where 'handle' is the handle of this figure that is assigned as follows:

h = figure(1);

Of course 1 can be any number you prefer. This way if the handle doesn't exist in the workspace, MATLAB would simply skip the 'ishandle' check and hence avoid the error.

[James Cai]

Should be: exist('h','var') && ishandle(h)

Answer 2

[Jorg Woehl]

R2014b and later no longer use numeric handles for graphics objects, so most answers given above do not work. In these cases, the following line of code will yield the figure handle to the desired figure:

handle = findobj(allchild(groot), 'flat', 'type', 'figure', 'number', nbrfig)

[Chris Schierer]

I'm not sure if this was broken for a while, and then fixed for backwards compatibility later, but in 2022b "ishandle" works for Figure objects and for legacy numeric integer figure handes.

>> qqq=figure(54)

qqq = 

  Figure (54) with properties:

      Number: 54
        Name: ''
       Color: [0.9400 0.9400 0.9400]
    Position: [1 1 1.6028e+03 741.2870]
       Units: 'pixels'

  Show all properties

>> ishandle(qqq)

ans =

  logical

   1

>> ishandle(54)

ans =

  logical

   1

Answer 3

[dpb]

Most basic is simply (assuming hfig is the handle you're looking for)

ismember(findall(0,'type','figure'),h)

sorts out from all figures whether the one is or is not valid.

ishandle(h) && findobj(h,'type','figure')==h

looks specifically for the one rather than brute force of findall() w/ the added complication must short-circuit if not valid to avoid error in findobj if passed invalid handle.

Many perturbations of the above ideas are possible, obviously...

[Jan]

ismember sorts the inputs for a binary search. For the small number of figures and for searching one handle only, ANY is faster. Searching all objects wastes time, because the figures are direct children of the root object. Therefore this is can be much faster, when many figures with many HG-objects are open:

any(findobj(allchild(0), 'flat', 'type', 'figure') == h)

Answer 4

[Jan]

Simpler and faster than using FINDOBJ:

ishandle(h) && strcmp(get(h, 'type'), 'figure')

Answer 5

[Gaëlle]

HI, Thank you for your answer, but actually a problem remains. I should have reformulated my question by saying "I want to obtain the handle of a figure without it appearing on the front", especially using the number of the figure rather than the name (so something exactly like findobj but where I could use the number of the figure as argument).

Answer 6

[Gaëlle]

Hi,

I did not know it was possible to simply use the number of the figure as the handle, for example get(120,'Position') would return the position of the figure(120). This is all I neeeded, thank you !

[dpb]

Well, for figures, the value of the handle is the same as the number of the figure. They're conceptually different but, the value '1' say will return false if it is anything other than a valid handle but any variable the evaluates to identically 1 will test T if there is, indeed a figure of that number extant.

Similarly for handles for other graphics objects; it's purely a numeric comparison for equality as far as can be determined by operations on the values.

'Preciate if could get an 'accepted' answer just to make the effort seem worth while... :)

[Gaëlle]

Answered accepted ;) thx!

Answer 7

[Evandson Dantas]

Try this

h = findall(0,'type','figure','name','figure_name');
if isempty(h)
   % Figure doesnt exist
else
   % Figure exist
end