I cannot access the handles in a timer callback function

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Kelly Babitz
Kelly Babitz 2017-7-30
编辑： Walter Roberson 2017-7-30
I have a GUI with a timer in it. I would like to be able to update a plot every .1 seconds, however, the timer function gives me the error:
Error while evaluating TimerFcn for timer 'timer-3'
Reference to non-existent field 'concMarker'
Can anyone help me fix this? I have been reading some other posts and people have been saying you need to update the handles structure, which I am not quite sure how to do (though when I have tried copying other people's code to do so it did not work either).
axis = findobj(PumpRateGuiDisplay,'Type','axes');
timerData = timer('TimerFcn',@timerFunction,...
'Period',.1,'ExecutionMode','FixedRate','BusyMode','Drop',...
'TasksToExecute',endTime*10 + 1,'Tag','timerData');
function timerFunction(hObject,eventData)
handles = guihandles(PumpRateGuiDisplay);
handles.cocnMarker = plot(axis,NaN,NaN,'r*');
timeElapsed = get(hObject,'TasksExecuted')-1;
if timeElapsed ~= 0
set(handles.concMarker,'XData',times(int64(timeElapsed*.1/timeIncrement)),'YData',concLeftVent(int64(timeElapsed*.1/timeIncrement)),'*');
end
end
Thanks in advance for the help!

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Walter Roberson
Walter Roberson 2017-7-30
handles.cocnMarker = plot(axis,NaN,NaN,'r*');
set(handles.concMarker,'XData',times(int64(timeElapsed*.1/timeIncrement)),'YData',concLeftVent(int64(timeElapsed*.1/timeIncrement)),'*');
Compare the name of the handle carefully between those two lines.
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Kelly Babitz
Kelly Babitz 2017-7-30
Thank you sooooooo much! I really appreciate the clear time and effort you spent on my question, I can honestly say you saved me many days of frustration and unproductiveness because I do not think I would have found this answer in a million years. I changed the next plot property for the axes to add and then put a hold on after my initial plotting of concMarker and now it works perfectly. Thanks again!
Walter Roberson
Walter Roberson 2017-7-30
编辑：Walter Roberson 2017-7-30
This was really obscure, and I had no idea that it happened.
I tend not to use imshow() because it changes too many properties for my liking, so I had never happened to encounter this before. It took digging.
I can see from the code that the behaviour is intended, but I filed a bug report anyhow to at least get it mentioned in the tips section.

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