Suppose you have a set of XY points. You plot them to see how they spread out. You decide a certain clump of points is special. How do you get MATLAB to know which points you care about? With lasso you can select them with your mouse!
To demonstrate I will use the sunspot example data that ships with MATLAB.
load sunspot.dat [x,y,i] = lasso(sunspot(:,1),sunspot(:,2))
press a KEY to start selection by mouse, LEFT mouse button for selection, RIGHT button closes loop x = 1836 1837 1848 1870 y = 121.5 138.3 124.7 139 i = 137 138 149 171
centroid = [mean(x) mean(y)]
centroid = 1847.8 130.88
The program prompted me how to start and stop the selection. I left off the semicolon to show the values returned for further analysis (ie, centroid calculation). The first plot shows the polygon region I selected. The second plot shows the selected points with a free legend and point counter. Nice!
Note: if you like graphically interacting with your XY points be sure to check out Data Brushing introduced with R2008a.
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