How to plot the vector relative black point to red point

Hello, I am a Matlab user beginner. I would like to seek your help about how to get the vector relative black point and red point. (like a black arrow). Thank you very much. The red position is red(x,y) =[25 257

64 181

64 334

68 31

105 257

106 104

107 410

147 181

147 334

148 28

149 487

189 104

189 257

189 410

229 181

230 28

230 333

230 486

269 104

271 410

272 257

313 28

313 181

313 334

313 486

354 104

355 257

355 410

396 180

396 334

397 28

397 486

438 104]

black postion(x,y) = [ 63 332

71 184

102 403

112 256

119 111

152 327

160 182

163 35

192 398

201 252

205 109

235 471

244 323

246 181

251 37

283 395

288 250

289 105

325 467

328 318

330 179

331 35

369 249

371 105

372 393

414 176

415 320

415 466

454 103

455 392

456 248

492 176

493 320]

[VBBV]

Take the distance between the two points on red and black vectors. Then Use quiver function to plot them

Answer 1

[Adam Danz]

1. Your [x,y] coordinates are not paired so step 1 is to find the values in black ('k') that are closest to red ('r') (or vise versa).
2. Some coordinates do not have close pairs. To detect and ignore those coordinates this solution thresholds the paired distances to 2 times the standard deviation of all distances and eliminates any pairs that exceed that distance from the mean distance.
3. This solution uses line() to plot lines between the final list of paired (x,y) coordinates.

% r and k are nx2 matrices of [x,y] coordinates
r =[25   64   64   68  105  106  107  147  147  148  149  189  189  189  229  230  230  230  269  271  272  313  313  313  313  354  355  355  396  396  397  397  438;
    257  181  334   31  257  104  410  181  334   28  487  104  257  410  181   28  333  486  104  410  257   28  181  334  486  104  257  410  180  334   28  486  104]';

k = [63   71  102  112  119  152  160  163  192  201  205  235  244  246  251  283  288  289  325  328  330  331  369  371  372  414  415  415  454  455  456  492  493;
    332  184  403  256  111  327  182   35  398  252  109  471  323  181   37  395  250  105  467  318  179   35  249  105  393  176  320  466  103  392  248  176  320]';

% Resort k according to proximity to r
dist = pdist2(r,k); 
[mindist, minIdx] = min(dist);  

% Eliminate connects that are greater than 2 std from mean distance
% This works for these data but may need tweeked for other data
eliminateIdx = mindist > mean(mindist) + std(mindist)*2;

% Store paired coordinates
rPair = r(minIdx(~eliminateIdx),:);
kpair = k(~eliminateIdx,:);

% Plot original data
clf()
hold on
scatter(r(:,1),r(:,2),50,'r')
scatter(k(:,1),k(:,2),50,'k')
axis equal
grid on

% Add connection lines
line([kpair(:,1),rPair(:,1)]', [kpair(:,2),rPair(:,2)]', 'Color', 'b')

●

Alternatively, you could use quiver as VBBV mentioned but it's important to set the scaling factor to 0 since you're working with exact end points of the vectors.

xDist = rPair(:,1) - kpair(:,1); 
yDist = rPair(:,2) - kpair(:,2); 

% Plot original data
figure()
hold on
scatter(r(:,1),r(:,2),50,'r') 
scatter(k(:,1),k(:,2),50,'k')
axis equal
grid on

% Add quiver arrows
quiver(kpair(:,1),kpair(:,2), xDist, yDist, 0, 'Color', 'b')

●

[Tina Hsiao]

Thanks a lot : )