compare 2 consequtive columns ?

2023 1 26
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更新时间：2023 1 26
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for example this 3x6 matrix
3 3 4 4 5 5
6 6 5 5 8 8
9 9 7 7 2 2
i want to compare two columns and display any changes in column , diplay number of times the changes occur .
the output should be
3 4 5
6 5 8
9 7 2
number times : 2

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Celestie Gladys
Celestie Gladys 2023-1-26
even though the last column dosent chage , it should be displayed ?
Fangjun Jiang
Fangjun Jiang 2023-1-26
You first and second column happen to be exactly the same. What if only one element changed, for example the second column is [3,10,9]'. Does it count as a change? What is the desired output? The number of changes? (in your case, 2)?
Celestie Gladys
Celestie Gladys 2023-1-26
@Fangjun JiangThe data I have changes the entire column, or it dosent change at all , so I asked about the entire column .

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Fangjun Jiang
Fangjun Jiang 2023-1-26
编辑：Fangjun Jiang 2023-1-26
Ran in:

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Ran in:
data=[3 3 4 4 5 5
6 6 5 5 8 8
9 9 7 7 2 2];
index=diff(data,1,2)
index = 3×5
0 1 0 1 0 0 -1 0 3 0 0 -2 0 -5 0
index2=any(index)
index2 = 1×5 logical array
0 1 0 1 0
output=sum(index2)
output = 2
OutData=data(:,[true,index2])
OutData = 3×3
3 4 5 6 5 8 9 7 2

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Celestie Gladys
Celestie Gladys 2023-1-26
@Fangjun JiangI require also to diaplay the changes in data like this ?
3 4 5
6 5 8
9 7 2
Les Beckham
Les Beckham 2023-1-26
Ran in:
Ran in:
data=[3 3 4 4 5 5
6 6 5 5 8 8
9 9 7 7 2 2];
unique(data', 'rows', 'stable')'
ans = 3×3
3 4 5 6 5 8 9 7 2
Fangjun Jiang
Fangjun Jiang 2023-1-26
See update in the Answer
Celestie Gladys
Celestie Gladys 2023-1-26
@Fangjun Jiang does it work for type double ?as it isnt working for me , the above is dummy data ,index and index2
Walter Roberson
Walter Roberson 2023-1-26
Those 0.0000 entries you see on output are locations where the output is not exactly 0, but is smaller than 0.0001 . If you were to configure your preferences for the variable browser to use "longg" format, then you would see the actual output more clearly.
Preferences -> Variables -> Format -> Default array format: long g
Preferences -> Command Window -> MATLAB Command Window Preferences -> Text display -> Numeric format: long g
The first of those controls the variable browser. The second of those controls "disp" and display of numbers triggered by not having a semi-colon after the computation.
Celestie Gladys
Celestie Gladys 2023-1-26
@Walter Roberson why does index=diff(data,1,2) dosent work and it suppose to generate [0,1]does it work on double ?
Walter Roberson
Walter Roberson 2023-1-26
Ran in:
Ran in:
diff() works fine on double, but your data might not be exactly what you think it is.
format long g
x = rand(1,10);
x(3) = x(2);
x(7) = x(6)*(1+eps);
x.'
ans = 10×1
0.891461741281098 0.631347191045054 0.631347191045054 0.516064708409579 0.824509730719412 0.720280713237283 0.720280713237283 0.96542744133625 0.503147047594 0.108609798103955
entry 3 should be exactly the same as entry 2, so we should see an exact 0 difference there
entry 7 displays exactly the same as entry 6, but is different in the final bits, so we should not see an exact 0 difference there
diff(x,1,2).'
ans = 9×1
-0.260114550236044 0 -0.115282482635475 0.308445022309833 -0.104229017482129 1.11022302462516e-16 0.245146728098968 -0.462280393742251 -0.394537249490044

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