# Use Double Array Values to Label Plot

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collegestudent on 28 Jan 2023
Edited: dpb on 29 Jan 2023
I have a variable 'xx' that is a 1x9 double. I want to use those values to label the points along the line in plot(t,xx)
This is my code
Ts = 1/8;
t = 0:Ts:1;
x = @(t) cos(2*pi*t-(pi/2));
xx = x(t);
labels = {'Sample 1', 'Sample 2', 'Sample 3', 'Sample 4', 'Sample 5', 'Sample 6', 'Sample 7', 'Sample 8', 'Sample 9'};
plot(t,xx,'rd-', 'linewidth', 1.5, 'MarkerSize', 9, 'MarkerFaceColor', 'w'), grid on
text(t,xx,labels)
##### 2 CommentsShowHide 1 older comment
collegestudent on 28 Jan 2023
But I also need to label each point with the correct sample number

dpb on 28 Jan 2023
"Would making labels = string(xx) work?"
Did you try?
It works for a basic definition of what "working" might mean; you might find something like
text(t,xx,compose('%0.3f',xx))
more pleasing to the eye. Investigate the named parameters to text regarding position the text so as to not write on top of the data itself...
##### 2 CommentsShowHide 1 older comment
dpb on 28 Jan 2023
Edited: dpb on 29 Jan 2023
Try something more like
Ts = 1/8;
t = 0:Ts:1;
xx = cos(2*pi*t-(pi/2)); % no need for the anonymous function here...
plot(t,xx,'rd-', 'linewidth', 1.5, 'MarkerSize', 9, 'MarkerFaceColor', 'w'), grid on
ylim(1.2*ylim)
hold on
labels=compose('Sample: %d\n%0.3f',[1:numel(xx)].',xx.');
hT=text(t+0.025,xx+0.05,labels);
hT(end).HorizontalAlignment='right';
hT(end).Position=[1-0.025 0.1];
for starters. One can always be more clever about trying to locate where place annotations based on actual data and anything known a priori about shape of curve, etc., to minimize occluding data more than necessary.
The fixup here for the last position to place it to the left instead of the right owing to knowing it will run off the RH side otherwise, is one obvious nicety.

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