Select only some coordinates from a .txt file

Question

Alberto Acri 2022-12-1

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1868488-select-only-some-coordinates-from-a-txt-file

评论： David Hill 2022-12-2

采纳的回答： David Hill

Hi!

I have the filename.txt file representing the coordinates of the nodes.

I have a nodes.txt file that represents the row I want to keep within the filename.txt file.

How can I locate the nodes I want?

For example:

the number 1 in the nodes.txt file represents the coordinate (307, 55) of the filename.txt file

the number 26 in the nodes.txt file represents the coordinate (308, 45) of the filename.txt file

and so on...

I want to bring back to the workspace only the coordinates of interest.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

David Hill 2022-12-1

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1868488-select-only-some-coordinates-from-a-txt-file#answer_1117348

在 MATLAB Online 中打开

n=readmatrix('nodes.txt');
m=readmatrix('filename.txt');
newMatrix=m(n,:)
newMatrix = 223×2
  55
  54
  53
  52
  51
  50
  49
  48
  47
  46

2 个评论
显示无隐藏无

Alberto Acri 2022-12-2

在 MATLAB Online 中打开

filename_3.txt

@David Hill could you help me with this code as well?

I would like to display only the red nodes.

data = readmatrix('filename_3.txt');
x = data(:,1);
y = data(:,2);
s = 1;
    
gap = 1;
yy = unique(sort(y));
ind = find(diff(yy)>gap);
val_low = yy(ind);
val_upper = yy(ind+1);
y_threshold = (val_low+val_upper)/2; % let's take the average of the two
    
% same approach to find x gap between left / right 
xx = unique(sort(x));
ind = find(diff(xx)>gap);
val_low = yy(ind);
val_upper = yy(ind+1);
x_threshold = (val_low+val_upper)/2; % let's take the average of the two
    
%upper left curve
idx = x<x_threshold;
idy = y>y_threshold;
x_temp = x(idx & idy);
y_temp = y(idx & idy);
k_UL = boundary(x_temp,y_temp,s);
x_out1 = x_temp(k_UL);
y_out1 = y_temp(k_UL);
      
%upper right curve
idx = x>x_threshold;
idy = y>y_threshold;
x_temp = x(idx & idy);
y_temp = y(idx & idy);
k_UR = boundary(x_temp,y_temp,s);
x_out2 = x_temp(k_UR);
y_out2 = y_temp(k_UR);
    
%lower left curve
idx = x<x_threshold;
idy = y<y_threshold;
x_temp = x(idx & idy);
y_temp = y(idx & idy);
k_LL = boundary(x_temp,y_temp,s);
x_out3 = x_temp(k_LL);
y_out3 = y_temp(k_LL);
    
%lower right curve
idx = x>x_threshold;
idy = y<y_threshold;
x_temp = x(idx & idy);
y_temp = y(idx & idy);
k_LR = boundary(x_temp,y_temp,s);
x_out4 = x_temp(k_LR);
y_out4 = y_temp(k_LR);
    
plot(x,y, '.', x_out1, y_out1, '.r', x_out2, y_out2, '.r', x_out3, y_out3, '.r', x_out4, y_out4, '.r')