Draw arrow in a plot

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Hi all, i have a question. I am creating a GUI that import real time data. I want draw a vertical line or a arrow if a condition is met.
For example:
n=length(p);
for i=1:n;
if p>100 && t>100
annotation=('arrow');
end
end
Is this correct for draw arrow in a plot in real time?
Thank you very much

Accepted Answer

Geoff Hayes
Geoff Hayes on 23 May 2015
Francisco - you may want to read the documentation on annotation. Your code of
annotation=('arrow');
would not work since you are assigning the string arrow to a variable called annotation. Instead you would want to do something like
X = [0.5 0.5];
Y = [0 0.5];
annotation('arrow',X,Y);
which would draw an arrow starting at the coordinate (0.5,0) and ending at (0.5,0.5). (Note that the coordinates are specified in normalized figure units which means that the arrow would be drawn in the middle.)
While you need not provide the X and Y inputs to this function, be aware that the default values will be used in place (of them) so the arrow may not be drawn where you expect it to be.
  6 Comments
francisco gonzalez
francisco gonzalez on 23 May 2015
Thank you very much Geoff. I am going to study this code and apply to my situation.

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