How do I put annotation text pointing towards specific coordinate?

Question

Samson David Puthenpeedika 2021-11-9

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1582844-how-do-i-put-annotation-text-pointing-towards-specific-coordinate

编辑： Matt J 2021-11-10

Below is my code , I have tried to put annotation text pointing towards a coordinate(3.4, 4.8248) using trial and error method . What is the proper way ?

x=[1 2 2.5 3 4 5]

x = 1×6

1.0000 2.0000 2.5000 3.0000 4.0000 5.0000

y=[0 5 7 6.5 2 0]

y = 1×6

0 5.0000 7.0000 6.5000 2.0000 0

A=3.4;Lagrange(x,y,A)

A = 3.4000

s = 0

c = 1×2 cell array

{[3.4000]} {[4.8248]}

ans = 4.8248

function yint=Lagrange(x,y,xx)

A=3.4

n=length(x);

s=0

for i=1:n

product=y(i);

for j=1:n

if i~=j

product=product*(xx-x(j))/(x(i)-x(j));

end

s=s+product;

end

yint=s;

figure()

plot(x,y)

hold on

scatter(A,yint,"x","b")

scatter(x,y,"o")

title('Lagrange Interpolation'); xlabel('x'); ylabel('f(x)');

c={A yint}

annotation('textarrow',[0.7 0.6],[0.7 0.64],'String',c)

hold off

legend('Interpolated Function','Result Point f(3.4)','Given Data');

hold off

end

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Answer 1

Matt J 2021-11-9

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1582844-how-do-i-put-annotation-text-pointing-towards-specific-coordinate#answer_827879

编辑：Matt J 2021-11-10

在 MATLAB Online 中打开

x=[1 2 2.5 3 4 5];

y=[0 5 7 6.5 2 0];

A=3.4;Lagrange(x,y,A);

function yint=Lagrange(x,y,xx)

A=3.4;

n=length(x);

s=0;

for i=1:n

product=y(i);

for j=1:n

if i~=j

product=product*(xx-x(j))/(x(i)-x(j));

end

s=s+product;

end

yint=s;

figure()

plot(x,y)

hold on

scatter(A,yint,"x","b")

scatter(x,y,"o")

title('Lagrange Interpolation'); xlabel('x'); ylabel('f(x)');

c={A yint};

%%%%%Matt J added

ax=gca;

xl=xlim;

yl=ylim;

xy0=[xl(1),yl(1)];

Dxy=[diff(xl),diff(yl)];

fn=@(xy) (xy(:)'-xy0)./Dxy.*ax.InnerPosition([3,4])+ax.InnerPosition([1,2]);

p=fn([3.4, 4.8248]);

%%%%%%

annotation('textarrow',[0.7 p(1)],[0.7 p(2)],'String',c)

hold off

legend('Interpolated Function','Result Point f(3.4)','Given Data');

hold off

end

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Samson David Puthenpeedika 2021-11-10

Oh thankyou ..understood now

Star Strider 2021-11-10

I like ‘fn’ and the supporting code!

+1

.

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Answer 2

Sulaymon Eshkabilov 2021-11-9

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1582844-how-do-i-put-annotation-text-pointing-towards-specific-coordinate#answer_827804

在 MATLAB Online 中打开

Here you can use the values of c to place where you want your annotation to be displayed along with the arrow. E.g.:

...
c={A yint}
annotation('textarrow',[c{1,1}, c{1,1}-0.07*max(x)]/max(x),[c{1,2},c{1,2}-0.07*max(y)]/max(y),'String',c)
...

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Matt J 2021-11-9

Sulaymon Eshkabilov's comment moved here

WIth the proposed solution, you don't need to find the coordinates by a trial and error. It takes up the found values of c. In other words, the annotation placement changes with respect to the calculated values of c.

Samson David Puthenpeedika 2021-11-10