# Use sorted variable to reorder rows of a matrix

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James Peach on 5 Jan 2021
Commented: James Peach on 5 Jan 2021
I am attempting to reorder the rows of a matrix from greatest number of nonzero elements to least. I calculate the number of zeros per row and then sort that variable to get the correct order, but I am having tourble using my sorted variable to reorder the original matrix. I have posted what I have so far below
Index_matrix = [42 33 27 22 17 12 7 4 2 1 0
43 34 26 21 16 11 6 3 1 0 0
44 35 28 22 17 12 7 4 2 1 0
45 36 29 23 18 13 8 2 1 0 0
46 37 30 24 19 14 9 3 1 0 0
47 38 31 25 20 15 10 5 2 1 0
48 39 32 26 21 16 11 6 3 1 0
49 40 33 27 22 17 12 7 4 2 1
50 41 31 25 20 15 10 5 2 1 0];
test = sum(Index_matrix==0, 2);
test2 = sort(test,1);
index_matrix = sort(Index_matrix, test2);
James Peach on 5 Jan 2021
Here is the full code that generated the matrix above. The matrix is stored under the handle master_index. All of this code builds on all the previous code I have posted on here for my research.
% 3D to 2D Mapping, Labeling, Rescaling
clear
close all
clc
%A = 50 pts
A = [0,0,0;0.00977495601952172,0.0129188554738323,0.999868768093125;-0.566794094824837,-0.823750570492204,0.0133959578031223;0.0279587435128966,0.0380588867245362,1.99938731654588;0.830388266617646,0.583999369869120,0.978401571089338;-1.07826433834531,-1.64452537544960,0.267810795303313;0.168715496407312,0.263085998125572,2.96351922435162;-0.791458202545459,0.611268411797120,0.998070417818667;-1.41124221175034,-0.289407593850698,0.0506110237693017;1.69942938355116,1.04462646221878,1.15892918358242;-1.55216375501531,-2.44987966243271,0.623934110066297;0.188310075544404,0.501770043093754,3.93441879647330;-1.44603145623221,1.35107113546187,1.15371676572365;-2.35391403973316,0.0183196401577155,0.179737992978120;2.59879677816763,1.38804628951095,1.42948622326796;-1.92629974765512,-3.28302931738291,1.03122259685150;0.190461468181228,0.731318108759712,4.90771374511875;-2.01837467713375,2.14014570650778,1.37684130228734;-3.30531517848174,0.217844651708771,0.414313445558867;3.50709118523837,1.65551615551852,1.75113998255253;-2.23204460424917,-4.13488361866807,1.45650407075820;0.193343935566412,0.934427321909631,5.88686559182864;-2.51244231909718,2.97180232130260,1.63030617210704;-4.25650570961388,0.357419056329789,0.689550723301627;4.41845060685608,1.87363023778730,2.10021053665969;-2.47842156351806,-4.99324597672323,1.90651791078471;0.204283419234320,1.13357858075284,6.86677329350173;0.617793464714887,0.0559247730198438,6.10612769252045;-2.96417360323821,3.81704174520463,1.91580426879081;-5.20242439373799,0.476408999682868,0.991344090368801;5.32672360772571,2.06445068867013,2.47253796167180;-2.69346338350278,-5.85030685131976,2.37470982965291;0.218591936197924,1.32878562119851,7.84743096960627;-3.26247612265381,-4.91985596911837,1.29018005288354;1.20197539596291,-0.580347098756520,6.61000225666269;-3.37592827171665,4.67443410026770,2.22457026832058;-6.14584567995603,0.584770610127789,1.30473528056482;6.23299868743130,2.22581272192086,2.86321400922248;-2.89467385558292,-6.70726873056154,2.84918921113506;0.209717491582492,1.53184472980862,8.82655723451965;5.28440710514136,1.17097130314088,2.91964410258613;0.576278852478300,2.24513662818586,7.66753960818188;-4.04653068178957,-4.84646596151352,0.673842194982372;1.72465217643194,-1.18852390077965,7.20743841278270;-3.76500316313530,5.53715317053961,2.54758193166533;-7.08499357301506,0.666849489054822,1.63829830698843;7.13773556686645,2.38268963160310,3.25924533904186;-3.08850223839479,-7.56458389242937,3.32609724340970;0.176682672356017,1.77636612069925,9.79563823738556;5.70892694024996,0.283366758099107,3.09836478191717];
SizeA = size(A,1);
x = A(:, 1);
y = A(:, 2);
z = A(:, 3);
figure
plot(x, y, '.', 'color', 'k', 'Markersize', 12,'MarkerEdgeColor','w');
for ii = 1:SizeA
t = text(x(ii),y(ii),num2str(ii));
t.Color = 'k';
end
title('3D to 2D Mapping XY Plane: Index Numbers');
xlabel('x')
ylabel('y')
%%
figure
plot(x, z, '.', 'color', 'k', 'Markersize', 12,'MarkerEdgeColor','w');
for ii = 1:SizeA
t = text(x(ii),z(ii),num2str(ii));
t.Color = 'k';
end
title('3D to 2D Mapping XZ Plane: Index Numbers');
xlabel('x')
ylabel('z')
%%
dist1a = nan(numel(x));
proximity = 1.000;
save_criteria = 3;
save_criteria2 = 2;
for i = 1:SizeA
for j = 1:(i-1)
dist1a(i,j) = sqrt((x(i)-x(j)).^2 + (y(i)-y(j)).^2 + (z(i)-z(j)).^2);
dist1a(j,i) = dist1a(i,j);
end
end
i2keep = find(sum((dist1a - proximity <= eps('single')), 2) >= save_criteria);
i2keep2 = find(sum((dist1a - proximity <= eps('single')), 2) >= save_criteria2);
keep_x1 = x(i2keep);
keep_y1 = y(i2keep);
keep_z1 = z(i2keep);
B = 1:SizeA;
index = ismember(B,i2keep2);
%%
col = 1;
[master_index,~] = find(~index');
master_index_size = size(master_index,1);
indx = zeros(master_index_size,1);
for i = 1:master_index_size
while master_index(i,end) ~= 1
col = col+1;
indx = master_index(i,col-1);
C = A(indx,:);
master_index(i,col) = knnsearch(A(1:indx-1,:),C);
if master_index(i,col) == 1
break
end
end
col = 1;
end
%master_index = flip(master_index,2);
%%
x_c = 0;
y_c = 0;
z_c = 0;
Center_Root = [x_c, y_c, z_c];
[x_dom,y_dom,z_dom] = sphere(80); % Create Sphere
x_dom = x_dom(41:end,:); % Keep top 41 x points
y_dom = y_dom(41:end,:); % Keep top 41 y points
z_dom = z_dom(41:end,:); % Keep top 41 z points
figure;
alpha 0.2
hold on
center_plane = [x_c, y_c]; % center point of circular plane
scale = 1;
s = 1*scale;
used_index = [];
h_SurfMatrix = [];
for i = 1:size(master_index,1)
branch = master_index(i,:);
branch(branch == 0) = [];
h = cell(numel(branch),1);
for j = 1:numel(branch)
if ismember(branch(1,j), i2keep)
s = s/2^(-1/3);
end
if ismember(branch(1,j),used_index)
h{j,:} = [];
continue
end
[x_loc,y_loc,z_loc, spheresXYZ{i,j}] = createspheres(A(branch(1,j),1),A(branch(1,j),2),A(branch(1,j),3), s);
h{j,:} = surf(x_loc+A(branch(1,j),1), y_loc+A(branch(1,j),2), z_loc+A(branch(1,j),3), 'FaceColor', 'k');
h = h(~any(cellfun('isempty', h), 2), :);
used_index = [used_index;branch(1,j)];
end
h_SurfMatrix = [h_SurfMatrix;h];
s = 1*scale;
end
%%
% Extract Surface XYZ Data
for i = 1:SizeA
Dx{i} = h_SurfMatrix{i}.XData;
Dy{i} = h_SurfMatrix{i}.YData;
Dz{i} = h_SurfMatrix{i}.ZData;
end
%%
% Concatenate Surface XYZ Data
Dx = cell2mat(Dx);
Dy = cell2mat(Dy);
Dz = cell2mat(Dz);
%%
function [X,Y,Z,spheresXYZ] = createspheres(spherex, spherey, spherez, s)
[x, y, z] = sphere(11);
X = (s*x)+spherex;
Y = (s*y)+spherey;
Z = (s*z)+spherez;
spheresXYZ = [X,Y,Z];
end

Akira Agata on 5 Jan 2021
test = sum(Index_matrix==0, 2);
[~, order] = sort(test);
Index_matrix = Index_matrix(order,:);
The result is like:
>> Index_matrix
Index_matrix =
49 40 33 27 22 17 12 7 4 2 1
42 33 27 22 17 12 7 4 2 1 0
44 35 28 22 17 12 7 4 2 1 0
47 38 31 25 20 15 10 5 2 1 0
48 39 32 26 21 16 11 6 3 1 0
50 41 31 25 20 15 10 5 2 1 0
43 34 26 21 16 11 6 3 1 0 0
45 36 29 23 18 13 8 2 1 0 0
46 37 30 24 19 14 9 3 1 0 0

KSSV on 5 Jan 2021
idx = [42 33 27 22 17 12 7 4 2 1 0
43 34 26 21 16 11 6 3 1 0 0
44 35 28 22 17 12 7 4 2 1 0
45 36 29 23 18 13 8 2 1 0 0
46 37 30 24 19 14 9 3 1 0 0
47 38 31 25 20 15 10 5 2 1 0
48 39 32 26 21 16 11 6 3 1 0
49 40 33 27 22 17 12 7 4 2 1
50 41 31 25 20 15 10 5 2 1 0];
id =sum(idx==0,2) ; % get the sum of zeros
[val,id1] = sort(id,'descend') ;
iwant = idx(id1,:)

R2019a

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