# How to display arc length of the line created on a line plot based on the input data

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Christopher Swain-Phipps on 17 Jan 2022
Answered: _ on 17 Jan 2022
Hi,
I am currently plotting a series of x and y co-ordinates using the plot(x,y) function in MATLAB which outputs a graph that looks something like this: How do I go about displaying the arc length of the line created at points along the line assuming my first x and y data point is 0% and my last data point is 100%?
##### 2 CommentsShowHide 1 older comment
jessupj on 17 Jan 2022
i think you want something along the lines of the cumulative sum of the pythagorean distances between successive points on the curve, normalized by the final term.

_ on 17 Jan 2022
% some x and y:
x = [10:-1:2 2:10];
y = [5+sqrt(x(1:end/2)) 5-sqrt(x(end/2+1:end))];
plot(x,y,'-o');
set(gca(),'XLim',[0 12]);
% calculate "normalized arc length":
dx = diff(x);
dy = diff(y);
ds = sqrt(dx.^2+dy.^2);
s = cumsum([0 ds]);
s = s/s(end);
% put a text at each x,y with value of s:
v_a = {'top','bottom'};
nx = numel(x);
for i = 1:nx
text(x(i),y(i),sprintf('%d%%',round(100*s(i))),'VerticalAlignment',v_a{1+(i>nx/2)});
end 