# How to remove duplicate x-values and rearrange the y-values?

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Marián Matejdes on 9 May 2022
Edited: Marián Matejdes on 16 May 2022
Dear Matlab users,
I would like to resolve with your help the following problem. I have multiple columns filled with x and y values in repeating order such as:
Col(1): x1 x1 x1 x2 x2 x3 x4 x4
Col(2): y1 y2 y3 y4 y5 y6 y7 y8
Col(n-1): x1 x1 x2 x3 x3
Col(n): y1 y2 y3 y4 y5
How would it be possible to rearrange the data into a form where the Col(1) would contain x-values without duplicates with corresponding y-values in the remaining columns? Something like:
Col(1): x1 x2 x3 x4
Col(2): y1 y4 y6 y7
Col(3): y2 y5 y4 y8
Col(4): y3 y3 y5
Col(5): y1
Col(6): y2
Your help is greatly appreciated. Thank you.
Marian

Marián Matejdes on 16 May 2022
Edited: Marián Matejdes on 16 May 2022
% raw_data matrix containing x, y, x, y, ... columns
new_data(:,1) = raw_data(:,1:2:end);
new_data(:,2) = raw_data(:,2:2:end);
% removing NaN values and sorting in ascending order
sort_data = sortrows(rmmissing(new_data));
% removing x-value duplicates, reduced matrix, unique with a small
% tolerance (it needs to be included)
[a,index] = uniquetol(sort_data(:,1));
% saving unique values into first column of uniqueMat
uniqueMat(:,1) = a;
% adding an extra row to index
index(length(index)+1) = length(sort_data)+1;
% filling the uniqueMat matrix with 0 and y-values
for i = 1:length(uniqueMat)
uniqueMat(i,(index(i)+1):index(i+1)) = sort_data(index(i):index(i+1)-1,2);
end
[R,S] = size(uniqueMat);
% picking up only the 2:S columns due to the possible 0 in the first column
X = uniqueMat(:,2:S);
% all elements of X equal to 0 will be converted to NaN
X(X == 0) = NaN;
% first column of uniqueMat filled with unique x-values
uniqueMat(:,1) = a;
% all other columns filled with y-values and NaN
uniqueMat(:,2:S) = X;
% creating final_data matrix filled with NaN
final_data = NaN(R,S);
% counting cells of uniqueMat which doesn't contain NaN with logical isnan
for i = 1:R
num_val(i,1) = S-sum(isnan(uniqueMat(i,:)));
final_data(i,1:num_val(i)) = rmmissing(uniqueMat(i,:));
end
% cropping the final_data matrix
final_data = final_data(:,1:max(num_val));

Walter Roberson on 9 May 2022
g = findgroups(x)
Col = splitapply(@(Y) {Y}, y, g) ;

Jonas on 9 May 2022
Edited: Jonas on 9 May 2022
use
yourMat=[ [4; 1; 1; 2; 3; 3; 5; 10 ], rand(8,4)];
[~,index]=unique(yourMat(:,1),'stable'); % get unique values from the first column of your matrix/cell without sorting the values
diminishedMat=yourMat(index,:)
diminishedMat = 6×5
4.0000 0.3450 0.5707 0.1908 0.5958 1.0000 0.8221 0.2884 0.4012 0.7886 2.0000 0.4300 0.0018 0.0691 0.2521 3.0000 0.5942 0.9363 0.3777 0.3080 5.0000 0.8913 0.4600 0.3938 0.3140 10.0000 0.7392 0.3923 0.4889 0.0321
Marián Matejdes on 9 May 2022
thank you for your answer, the problem is that the information represented by y-values is reduced. yourMat contains 8x4 y-values, while diminishedMat only 6x4. The information wouldn't be reduced if row(2) and row(4) of diminishedMat would contain 9 elements including the one x-value.

R2021b

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