How to plot entire row of numerical matrix from corresponding logical array?

I have a 176496x3 double numerical matrix (A) comprised of 3D coordinate point data. I used the 'ischange' function on matrix A - the output is a 176496x3 logical matrix (A_changed). From there I isolated the nonzero points and was given a 467x1 logical matrix (A_nonzero).

The 467 nonzero values correspond to 467 values detected by the 'ischange' funtion. The values are not full coordinate points.

How can I plot (on a 3D plane), not just the 467 individual coordinates, but the entire rows (xyz-coordinate/3D point) that they come from?

An example of what I mean:

A =

[0.220, 0.0095, -0.2745;

0.2210, 0.009, -0.2744;

0.2218, 0.009, -0.2745;

0.2215, 0.0095, -0.2744;

0.2215, 0.0085, -0.2743]

A_changed =

[0, 0, 0;

0, 1, 1;

0, 1, 0;

1, 0, 1;

0, 0, 1]

A_nonzero =

[1;

1;

1;

1;

1;

1]

In this example, I want to plot

A_final =

[0.2210, 0.009, -0.2744;

0.2218, 0.009, -0.2745;

0.2215, 0.0095, -0.2744;

0.2215, 0.0085, -0.2743]

Additionally, here is the code I'm using:

% The data is imported from a file titled Drill
A = Drill;
A_changed = ischange(A, 'linear', 'Threshold', 0.01);
B = A_changed > 0;
A_nonzero = A_changed(B);

Attached is a small sample of the data (100 points). I made sure there are at least 5 rows with values detected by the 'ischange' function. I can also provide the full set of data as an .xyz file if that is preferred.

Lastly, I'm using Matlab R2021a.

Answer 1

[Kevin Holly]

Drill = [ 0.2324    0.0010   -0.2805
    0.2324    0.0005   -0.2805
    0.2322         0   -0.2800
    0.2324         0   -0.2805
    0.2325    0.0005   -0.2806
    0.2325    0.0010   -0.2808
    0.2325         0   -0.2809
    0.1840    0.0046   -0.2640
    0.1840    0.0050   -0.2643
    0.1835    0.0050   -0.2640
    0.1850    0.0050   -0.2643
    0.1845    0.0051   -0.2645
    0.1845    0.0050   -0.2642
    0.1850    0.0051   -0.2645
    0.1852    0.0050   -0.2645
    0.1841    0.0045   -0.2640
    0.1845    0.0045   -0.2642
    0.1850    0.0045   -0.2642
    0.1855    0.0045   -0.2641
    0.1855    0.0047   -0.2645
    0.2266    0.0005   -0.2760
    0.2250         0   -0.2756
    0.2255         0   -0.2758
    0.2260         0   -0.2759
    0.2265         0   -0.2760
    0.2265         0   -0.2760
    0.2278         0   -0.2760
    0.1618    0.0040   -0.2570
    0.1620    0.0040   -0.2568
    0.1620    0.0041   -0.2570
    0.1600    0.0050   -0.2577
    0.1600    0.0055   -0.2577
    0.1595    0.0050   -0.2575
    0.1595    0.0055   -0.2577
    0.1616    0.0045   -0.2575
    0.1620    0.0045   -0.2573
    0.1620    0.0047   -0.2575
    0.1600    0.0045   -0.2576
    0.1595    0.0045   -0.2575
    0.1613    0.0040   -0.2575
    0.2315   -0.0045   -0.2780
    0.2320   -0.0042   -0.2780
    0.2318   -0.0045   -0.2775
    0.2320   -0.0043   -0.2775
    0.2315   -0.0045   -0.2780
    0.2317   -0.0040   -0.2780
    0.2315   -0.0050   -0.2775
    0.2315   -0.0045   -0.2780
    0.2315   -0.0045   -0.2780
    0.2320   -0.0042   -0.2785
    0.2320   -0.0042   -0.2790
    0.1320    0.0019   -0.2480
    0.1320    0.0020   -0.2482
    0.1316    0.0020   -0.2480
    0.1342    0.0020   -0.2485
    0.1340    0.0020   -0.2480
    0.1341    0.0020   -0.2480
    0.1340    0.0021   -0.2485
    0.1325    0.0017   -0.2480
    0.1325    0.0020   -0.2482
    0.2331   -0.0215   -0.2780
    0.2330   -0.0220   -0.2777
    0.2330   -0.0222   -0.2775
    0.2333   -0.0215   -0.2785
    0.2334   -0.0210   -0.2785
    0.2335   -0.0210   -0.2787
    0.2335   -0.0207   -0.2785
    0.2340   -0.0210   -0.2788
    0.2340   -0.0205   -0.2785
    0.2335   -0.0215   -0.2789
    0.2335   -0.0216   -0.2785
    0.0508         0   -0.2170
    0.0510         0   -0.2166
    0.0510    0.0003   -0.2170
    0.0515         0   -0.2168
    0.0515    0.0002   -0.2170
    0.0517         0   -0.2170
    0.0505    0.0001   -0.2175
    0.0505         0   -0.2174
    0.0510    0.0004   -0.2175
    0.2333   -0.0355   -0.2720
    0.2322   -0.0360   -0.2720
    0.2325   -0.0357   -0.2720
    0.2330   -0.0356   -0.2720
    0.2215   -0.0560   -0.3115
    0.2215   -0.0559   -0.3115
    0.2215   -0.0560   -0.3114
    0.2216   -0.0560   -0.3115
    0.2215   -0.0559   -0.3120
    0.2215   -0.0560   -0.3120
    0.2220   -0.0560   -0.3116
    0.2220   -0.0557   -0.3120
    0.2025   -0.0595   -0.3165
    0.2025   -0.0595   -0.3165
    0.2025   -0.0595   -0.3165
    0.2030   -0.0595   -0.3163
    0.2030   -0.0594   -0.3165
    0.2034   -0.0595   -0.3165
    0.2040   -0.0595   -0.3163
    0.2040   -0.0595   -0.3160];


% The data is imported from a file titled Drill
A = Drill;
A_changed = ischange(A, 'linear', 'Threshold', 0.01);


% B = A_changed > 0;
row(:,1) = sum(A_changed,2);
row(:,2) = 1:length(row);
rows2plot = row(row(:,1)>0,:);

figure
subplot(1,3,1)
plot3(A(rows2plot(:,2),1),A(rows2plot(:,2),2),A(rows2plot(:,2),3))
subplot(1,3,2)
scatter3(A(rows2plot(:,2),1),A(rows2plot(:,2),2),A(rows2plot(:,2),3),'r','filled')
subplot(1,3,3)
plot3(A(rows2plot(:,2),1),A(rows2plot(:,2),2),A(rows2plot(:,2),3))
hold on
scatter3(A(rows2plot(:,2),1),A(rows2plot(:,2),2),A(rows2plot(:,2),3),'r','filled')

[Marina Baltz]

This worked perfectly, thank you! If you don't mind though, can you please explain what this part of the code is doing?

row(:,1) = sum(A_changed,2);
row(:,2) = 1:length(row);
rows2plot = row(row(:,1)>0,:);

Just trying to better my understanding for the future :)

[Kevin Holly]

The first line sums the rows and saves the vertical vector to the first column of variable row

row(:,1) = sum(A_changed,2);

by default sum(A_changed), would sum the columns;

sum(A_changed,1) also sums the columns;

I created an index for each of the orignal rows, naming them 1,2,3,4....until I reach the last index position (in this case is 100), which is equal to the length(row) or size(row,1). I could have also made it the length(A_changed) or size(A_changed,1).

row(:,2) = 1:length(row);

Next, I converted that sumed vertical vector that may have values greater than 1 (could be 2 or 3) to a logical array of ones and zeros.

row(:,1)>0

I used that logical array to select the rows I will use.

rows2plot = row(row(:,1)>0,:);

logical_array = row(:,1)>0

row(row_selection,column_selection)

the colon (:) selects all points

logical array selects all points with value of 1 (true)

so you can view it as:

rows2plot = row(logical_array,:)

rows2plot =

1 41

1 52

1 61

2 72

2 81