How to find coordiates of the LAST point of the aray which has been plotted?

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Dima
Dima 2014-8-10
评论： Image Analyst 2014-8-12
Hello! I have plotted a few time series on a graph. I need to be able to crop out a certain a fixed part (rectangle area 1000x1000 pixels) For this I was able to find this code:
imagesize=size(I);
xsize=imagesize(1,2)
ysize=imagesize(1,1)
xziseout=xsize-xsize*0.3
yziseout=ysize/2-ysize/5;
I2 = imcrop(I,[xziseout yziseout 1000 1000]); % [xmin ymin width height]
imshow(I)
figure, imshow(I2)
print('-dpng', printnamepngfile, '-r350')
I am using this code to roughly get the area out of the center of the picture but it fails because I actually need to focus on cpecific pixel. This pixel is the last point of a plotted array. I wonder how I can get pixel coordinates of the last data point that was plotted n a chart. I need these XY coordinates to be relative to the absolute pixel height and width of the output picture.
Thanking many times for any help in this matter!!!
Dima

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回答（2 个）

Image Analyst
Image Analyst 2014-8-10
You forgot to attach the picture. I don't know if you have an image, or if you have some kind of 1D data plotted as a line chart in an axes, or an image of a graph. I don't understand why you say "plotted". Generally images are "displayed", not "plotted". And I don't know what you mean by the last point. Do you mean I(end, end), or I2(end, end)????
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Dima
Dima 2014-8-12
Do you think this kind of task can be accomplished in principle???? I need it a lot to complete the current assignment....thank you!

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Michael Haderlein
Michael Haderlein 2014-8-12
So I believe you know the position inside the axis you want to focus, right? Let's say you've plotted something between x=100:102 and y=-90:-88 and you want to get the position of the center point (101,-89). You first need the relative position inside the axis and then get the absolute position (e.g. in pixels):
figure, axes, plot(100:102,-90:-88)
x=101;y=-89;
lim=get(gca,{'xlim','ylim'});
xfrac=(x-lim{1}(1))/diff(lim{1});
yfrac=(y-lim{2}(1))/diff(lim{2});
ax_units=get(gca,'units');
set(gca,'units','pixels');
ax_pos=get(gca,'position');
x_abs=ax_pos(1)+xfrac*ax_pos(3)
y_abs=ax_pos(2)+yfrac*ax_pos(4)
set(gca,'units',ax_units)
Hope this helps.

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