Scatter and line problem

Question

Krasimir Terziev 2020-3-12

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/510554-scatter-and-line-problem

评论： Krasimir Terziev 2020-3-12

采纳的回答： the cyclist

在 MATLAB Online 中打开

Hello

i have a little problem with this two functions : scatter and line

Here is a simple code that i write:

x=[16.3,7.3,3.3,13.3,2.3,6.3,12.3,16.3,5.3,12.3,7.3,19.3];
y=[6.7,17.7,7.7,18.7,6.7,13.7,4.7,17.7,17.7,9.7,9.7,16.7];
figure(1)
scatter(x,y,'o')
grid

These are four things i need to find out :

1. i cant find out how to connect a random points of this data ?

EXAMPLE : i need a line between 1st data (x=16.3, y=6.7) and (randomly hmmm) 8th date (x=12.3, y=9.7), then i want to connect the 8th and 6th data point and etc....

2. How to make a bigger circle around the "o" simbol with a radius that i want ?

3. How can i measure the line between the 1st data and the 8th data?

EXAMPLE: i can do this manualy whit Pythagorean theorem but i need to find a function to do it and a way to write above the line the length.

4. how can i write a random text above all data point ?

EXAMPLE: above point 1 ( 1st data x=16.3, y=6.7) i want to write a Village One (for example) !

THANKS YOU ALL ! WISH YOU BEST !

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Answer 1

the cyclist 2020-3-12

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/510554-scatter-and-line-problem#answer_419850

编辑：the cyclist 2020-3-12

在 MATLAB Online 中打开

This code illustrates everything you asked about.

% Fix the random number seed, for reproducibility
rng default
% Data
x=[16.3,7.3,3.3,13.3,2.3,6.3,12.3,16.3,5.3,12.3,7.3,19.3];
y=[6.7,17.7,7.7,18.7,6.7,13.7,4.7,17.7,17.7,9.7,9.7,16.7];
% Choose random point to connect to point 1.
rn = randi(8);
% Distance to that point
d = pdist([x(1)  y(1); ...
           x(rn) y(rn)]);
figure(1)
% Scatter plot (with larger marker)
scatter(x,y,'o','SizeData',500);
% Connect point 1 to the randomly selected one
line([x(1) x(rn)],[y(1) y(rn)]);
% Write the distance
text(15,5,sprintf('d = %7.3f',d))
% Add the grid
grid

The only thing I did "manually" was hard-code the values where the text appears, so that it is near the drawn line. Instead, one would want to calculate the position of that text via the locations of the two points, and putting it near the halfway point.

Note also that I used the sprintf function to convert a numeric value to text, before writing it. If you just have some known text, you can just do

text(x,y,'Known text')