How do I add refreshable text label to my plot?

Hello,

After searching the web and the Q/A in your site I have decided to beat the experts. I am creating bar figure and I would like to see the value on top of each bar. My problem is that my figure refreshes every 2 seconds via timer (which is good), but the text on the bars is accumulating. I tried all values of 'erasemode' but it didn't help. I also tried to do h = text(...) and then delete h, but it didn't solve anything. Sorry to disturb if there is a similar question and solution.

Thanks in advance, Liad.

Answer 1

[Laura Proctor]

I tried the following and it worked:

 h = text(1,1,'hi there')
 delete(h)

So I'm wondering if you would be able to show a simple example to help explain the issue.

Answer 2

[Fangjun Jiang]

set(h,'String','this is new text')

Answer 3

[sco1]

The way your question reads, I'm assuming you are annotating the plot itself using the text() function?

Are you using hold?

[Liad]

Thanks for the quick answers!

As I mentioned, I would like the text to get refreshed every cycle.

For now it works partially, and when I add 'h(patIx) = text', it doesn't work at all.

Any ideas?

Thank you.

Here is a part of my code:

% Declare the handles once

persistent hbar;

persistent h;

persistent ht;

%initialize

if isempty(hbar)

for patIx = 1:6

h(patIx) = subplot( 6, 1, patIx,'Parent',handleAxes );

hbar(patIx) = bar(lineNum, data(:,patIx), 0.01,'Parent',h(patIx));

end

end

try

for patIx = 1:6

set (hbar(patIx), 'XData', lineNum);

set (hbar(patIx), 'YData', data(:,patIx));

if ~isempty(ht)

delete (ht);

end

ht = text(lineNum, data(:,patIx),num2str(data(:,patIx)), 'Parent', hbar(patIx),'EraseMode','background');

end

catch

disp('Error in plot 6 subplots');

end

[Laura Proctor]

One thing that I see you are testing is if ht isempty. This probably isn't the way to test. Perhaps a test such as ishandle would be more appropriate. Because once you delete ht, it does still exist and will contain a number, it's just that it's no longer a handle object.

[Fangjun Jiang]

I don't understand. If you want to change the string of your text element and you have its handle, why can't you use

set(ht,'String',num2str(data(:,patlx)))

[Liad]

Hi,

I tried to move the next line to my initialize section, and do the 'set' in the 'for' loop:

ht(patIx) = text(lineNum, data(:,patIx),num2str(data(:,patIx)), 'Parent', hbar(patIx),'EraseMode','background');

But it keeps crashing even in the initialize part.

Does the 'set' allow to change the position of the text? Because I would like it in the height of my bar each time the plot gets refreshed.

Thank you,

Liad.

[Fangjun Jiang]

Once you created the text() element and get its handle ht(patlx), you can type get(ht(patlx)) in the Matlab command window to see all its properties. Then you can use set() to change most of the properties.

Start with the simplest option to create the text() element, step through to understand how it works and gradually add more options.

What do you mean "crashing"? Does it cause errors? or the figure does not show correctly? use the command drawnow() may help refreshing the figure.